It's rare that a whistleblower who has been so outrageously wronged by a large company – in this case Ireland's largest bank, AIB – ends up being so publicly vindicated.

Until 2002, Eugene McErlean, as head of AIB Group audit, was the bank's most senior internal policeman. AIB then wrongly linked him with the failures of others to stop rogue trader John Rusnak at its Allfirst Bank in the US. He had little choice to leave the bank.

It appears McErlean made big enemies because he did his job well. He helped uncover systematic overcharging of customers at AIB branches and queried a maze of on-shore and offshore hidden companies that Goodbody Stockbrokers used for about a decade.

McErlean hasn't worked since leaving the bank in 2002.

As the Sunday Tribune has previously reported, he was not the first head of audit whose career has been interrupted at AIB.

At a second hearing of the Oireachtas economic regulatory affairs committee last Thursday, McErlean extracted an apology from departing AIB chief executive Eugene Sheehy for the way the bank treated its most senior auditor.

But the questions that McErlean raised at an earlier committee hearing, about the regulatory system here and about other disclosures spanning the previous decade, have been left hanging in the air.

McErlean revealed that Goodbody used a network of off-shore companies to trade AIB shares. The Sunday Tribune reported in late March that Goodbody had operated other hidden accounts and companies to trade a wide range of shares out of sight of regulators and supervisors dating back to the sale of government shares in Irish Life in the early 1990s.

Company law was mysteriously changed in 2001 to make questionable Goodbody share trading in AIB shares legally watertight.

This newspaper also linked a nominee shell company used by Goodbody to a Charter House company in the Isle of Man, which had links with people who helped to hide the beneficial ownership of Yukos oil giant in the late 1990s.

Other links exist between Charter House nominee companies and off-shore nominee companies used by Frank Dunlop.

Last week AIB's Sheehy said the Isle of Man companies were "funded" by an unnamed fund manager.

Thursday's public hearing heard well-informed questioning from Senator Shane Ross and TD Fergus O'Dowd, who raised questions about the sale of government-owned shares in Irish Life by Goodbody in the early 1990s.

But O'Dowd has also asked a crucial question: how could company law be so easily changed at the bidding of AIB when even the bank became concerned about the labyrinth of offshore nominee companies it set up linking the Isle of Man and the hermetically-sealed financial centre Nevis, in the Caribbean?

Eugene McErlean and his AIB career

Born: 1958, Antrim town.

Educated: St Malachy's College, Belfast; primary and postgraduate degrees in law at Queen's University Belfast.

Law career: Corporate lawyer with the North's old Industrial Development Board; from 1986-1991 worked as a lawyer with future BA chief executive Bob Ayling at Heathrow airport. Joined AIB Group in 1991 as secretary and legal adviser, and compliance officer of First Trust Bank in Belfast.

1997: Appointed AIB Group head of internal audit at Bankcentre in Dublin.

1997-2002: Helped oversee various internal investigations and reports into overcharging AIB retail customers and questionable Goodbody share trading schemes.

2002: Left AIB after the bank, in a press release, linked his departure with the $691m losses made by rogue trader John Rusnak at its Allfirst Bank in the US.

July 2008: After battling for years with the Data Commissioner through the circuit court for disclosure of the minutes of a meeting with the regulator, the McErlean family writes to TD Fergus O'Dowd, Senator Shane Ross and others seeking their help.

21 May 2009: Departing chief executive Eugene Sheehy apologises for the treatment of McErlean.