It's a horrific story of alleged child abuse, lies, inaction that potentially placed countless Irish children at risk for over two decades, and a cover-up which is still continuing. Sinn Féin member and suspected paedophile Liam Adams was moved around Ireland in the same way that abusing Catholic priests went from parish to parish.

Gerry Adams has believed for 22 years that his brother is a paedophile. Yet he attended his wedding, took him canvassing for Sinn Féin in Dundalk, allowed him to remain active in the party – and lied about it.

He knew Liam was working with children in various youth projects. Yet despite his public claims, he has as yet produced no evidence to prove that he took action to have Liam removed by his employers.

Liam Adams is facing 23 charges in the North of raping and abusing his daughter, Áine Tyrell, between 1978 and 1983. Áine reported the alleged rapes to the RUC in 1987.

Gerry Adams' disturbingly inadequate response to his brother's suspected abuse makes him politically toxic. He is stripped of all credibility and moral authority. His position as a public figure is untenable. Were he the leader of any other party, he would have resigned by now. Would Brian Cowen, Enda Kenny, Peter Robinson or Mark Durkan survive such damning revelations? Not a chance.

Yet Gerry Adams defiantly holds onto the reins of power. In any other party, there would be uproar in the ranks with senior colleagues demanding he go. In Sinn Féin, not a single voice of even mild complaint has been raised. Indeed, Mary Lou McDonald – presented as a champion of women's and children's rights – has strongly defended him.

Since Áine went public about her father Liam's alleged abuse on UTV's Insight programme 10 days ago, Gerry Adams' account of events has been littered with lies, evasions and inconsistencies. The Sinn Féin president has many serious questions to answer. Áine told him of the alleged rapes in 1987. He said he believed her.

Gerry Adams' first lie was that he was estranged from his brother for 15 years. This "estrangement" is said to have lasted until 2002-2003. Yet the Sunday Tribune has discovered the opposite.

He attended Liam's wedding and reception in the Bellingham Castle hotel in Co Louth. How can Gerry Adams justify attending the wedding of a brother he believed to be a paedophile? How can he stand smiling beside Liam for the wedding photographs when he knows Áine is a wreck, barely able to sleep at night?

Gerry Adams also lied about his brother's activities in Sinn Féin in Dundalk. Liam Adams lived and worked in Muirhevnamor, a well-known republican estate to which many Belfast IRA members on the run moved.

The Sunday Tribune last week reported he had sought the nomination to be Sinn Féin's Co Louth candidate in the 1997 Dáil election, which was won by local hardline republican Owenie Hanratty. Sinn Féin comprehensively denied this. Gerry Adams said that as soon as he had heard Liam might be nominated, he intervened: "I moved immediately both to stop that and to get him dumped out of Sinn Féin... I moved very, very quickly."

Today, we expose this as a lie. Far from having Liam "dumped" from the party, Gerry Adams accompanied his suspected paedophile brother on a Sinn Féin canvass through Dundalk town centre just days before the 6 June election. The Sunday Tribune has uncovered photographs and a newspaper report of the event. The brothers are seen laughing on the canvass – more proof that they were not "estranged".

We have also statements from three republicans who were present at the selection convention in the Imperial Hotel, which Sinn Féin still denies took place. It was chaired by Caoimhghín Ó Caoláin and minutes were taken, the sources said. Liam Adams was supported mainly by Belfast republicans living in Dundalk who were moderate and pro-leadership.

Local Dundalk republicans, and south Armagh men living in Co Louth, rallied behind Hanratty. After a debate, it was agreed that IRA activists and republican supporters who weren't in Sinn Féin could vote at the meeting.

"The room was jam-packed," one source said. "Liam Adams came in with two envelopes. I'm told one was an acceptance speech and the other was one of him conceding. He immediately saw from the crowd gathered that he wouldn't win, so he pulled out. A massive show-of-hands defeat would have damaged his brother."

Another source said: "Liam announced to the room that he was withdrawing from the race. He wished Owenie Hanratty all the best, pledged to work for him on the election campaign, and they shook hands."

Sinn Féin claims Liam's involvement in the party in Dundalk was brief, but republican sources insist it lasted at least seven years. One source said Gerry Adams regularly visited his brother in Muirhevnamor, staying overnight in his home many times.

Liam Adams was strongly drawn to jobs that provided access to young people. He constantly sought and, with incredible success, secured them in west Belfast and Dundalk. Questions must be asked as to who provided references for him and who sat on the interview panels.

Gerry Adams said that when he became aware of some of the jobs Liam held, he took action to inform the relevant authorities. He has so far produced no written record of this. Nor has he disclosed the names of those he spoke to in the projects Liam worked for, or of those he spoke to in social services.

None of Liam Adams' four employers has said they were contacted by Gerry Adams. Indeed Brendan Dineen of Clonard Youth Centre said it had reviewed all its documentation "and there is no record whatsoever regarding concerns about Liam Adams during his time of employment at Clonard".

The youth centre, located in the grounds of Clonard Monastery, is 300 yards from Sinn Féin's Falls Road offices where Gerry Adams would have visited almost every day on party business. He also worships in the monastery. It is inconceivable that, for five years, he didn't quickly know his brother worked in Clonard.

Gerry Adams has a close relationship with certain priests in the monastery who were intimately involved in the peace process. Solicitor Pádraigín Drinan, who represents the Rape Crisis Centre, has one disturbing memory from around 10 years ago at the annual Clonard novena in June.

Worshippers write down their 'intentions' and a panel selects which are read out from the altar.

"One intention asked for a person who had made allegations of sexual abuse to police to forgive the man involved and withdraw the complaint. I was appalled," Drinan says. She complained to the monastery.

If the Sinn Féin president was genuinely concerned that his brother was securing so many jobs working with young people, why didn't he make those concerns public? He didn't have to compromise his niece's identity. A statement could simply have outlined that his brother was unsuited to working with young people. But that would have risked public embarrassment. In­stead, Gerry Adams stayed silent and his own west Belfast constituents were potentially put at risk from his suspected paedophile brother.

Gerry Adams must also explain why, in his 1996 autobiography, Before the Dawn, he made 11 references to "our Liam" with no insinuation of suspected wrongdoing. Did he not think this might deeply upset Áine?

Did Gerry Adams not read Republican News, his party's official newspaper, which in 1997 advertised a pamphlet his brother had written on drug abuse among children? Why didn't he take action as Liam repeatedly gave interviews on youth issues to a range of newspapers, including the Irish News, the Mirror and the Irish Independent, thus allowing Liam to build his reputation in that field?

An Irish News article of 6 August 2006 reports: "A parents' guide to drugs and alcohol written by Sinn Féin president Gerry Adams' brother was launched in west Belfast yesterday." Liam Adams is quoted speaking at the launch. Why didn't the Sinn Féin president swiftly distance himself from his brother and his spiralling public profile as a youth worker?

Gerry Adams' personal response after Áine's revelations has been criticised by sexual abuse counsellors. In 1987, he drove his vulnerable 14-year-old niece to Donegal to confront her father who was living there. They sat down to tea and Mikado biscuits.

Áine's family say that, while Gerry Adams was sympathetic at first, his attitude changed in Donegal. When Liam denied the allegations and Áine persisted, Gerry Adams is said to have stated: "it's like trying to prove who stole the apples from the cart".

Sinn Féin had a vibrant women's department. Why didn't Adams seek and implement their advice – still without revealing his niece's identity – about how to handle the situation?

When Áine again raised the issues of the rapes with Gerry Adams in 2003 – wanting her father to admit his crimes to her – a five-year period of secret meetings began with Gerry and his brother Paddy Adams. Áine's family now believe the meetings were to shut her up by giving her false hope. Eventually, she ended the meetings.

"When I heard Áine talk about those endless, useless meetings, I remembered how Sinn Féin had done the same to us in the early stages of our campaign, using double-speak and trying to 'handle' us," said Catherine McCartney, whose brother Robert was murdered by Provisional IRA members. "My heart went out to her."

There are other questions too. Áine reported the alleged rapes to the RUC in 1987. If they didn't already know about them, MI5 learned of Liam Adams' reported crimes then. British intelligence had a perfect opportunity to leak these details to harm Gerry Adams, the most influential Sinn Féin and IRA figure in Ireland. They didn't, and many republicans are now asking why.

Then there's the IRA's response. An ex-prisoner said: "Liam Adams escaped scott-free, while the IRA has tied women to lamp-posts, cut off their hair, and tarred and feathered them for simply dating British soldiers."

Why was Liam Adams a protected species when other alleged sex offenders were maimed and murdered by the IRA?

Paddy Adams, Gerry's brother, enjoyed similar immunity in republican ranks. In the 1980s, he hired IRA guns to criminals in west Belfast for money. One ex-IRA member said: "Anyone else would have been shot or expelled. Nothing happened to Paddy."

Gerry Adams' revelation that his father, Gerard Senior, was a sex abuser shouldn't divert attention from the Sinn Féin president's lies and shameful behaviour following the reported rape of his niece. Of course, he shouldn't be held responsible for his brother. What he can be blamed for is 22 years of putting the Adams name before the protection of children on both sides of the border, children he has always claimed to care so much about.