IT kicked off shortly after 11pm last Sunday night and after a week of back-biting it hasn't gone away you know. The public spat between Sinn Féin and the Labour Party already looks set to be a dominant feature of Election 2011.

On RTé's The Week in Politics programme, presenter Sean O'Rourke asked Labour TD Roisín Shortall why Labour wanted to go back into coalition with Fine Gael when they could go in with Sinn Féin and other left-leaning parties.

Shortall responded that her party wanted to do "the right thing by this country" and ensure a stable government. She said, "the Labour Party's ultimate aim is a left-led government" but "any such government would require the support of a rag-bag collection of independents… I am talking about the kind of hard-left groupings that are forming. It is not in the interests of the country that you would have that kind of rag-bag government."

Shortall's comments sparked an immediate angry reaction from Sinn Féin's Martin Ferris who replied: "It's amazing that she is talking about the ultra-left and a rag-bag. Democratic Left was part of a government and Democratic Left now controls the Labour Party and that is a reality.

"You had Official Sinn Féin, Sinn Féin The Workers Party, Democratic Left and now the Labour Party and they went into government and they were accepted by Fianna Fáil and Fine Gael. The derogatory words you used to describe political opponents are disgraceful."

The joust between Shortall and Ferris has kicked off an intriguing wider battle between the two opposition parties.

Conventional wisdom suggests that Labour is certain to go into government with Fine Gael and the only issue to be determined by the campaign is the breakdown of seats between the two likely coalition partners.

The 'Gilmore Gale' is still on the cards and it is highly likely that Eamon Gilmore will lead the Labour Party to win more Dáil seats than the 33 won under Dick Spring's leadership during the 1992 'Spring Tide'.

But there is also a school of thought that Labour has had a crisis of confidence in recent weeks and there is a chance that it could get squeezed in the election between Fine Gael on the right (who will garner middle-class votes) and Sinn Féin on the left (which is battling for disaffected working-class votes).

There is a view that Labour was riding high on a cloud of self-confidence until the end of November, when Sinn Féin's Pearse Doherty had a resounding victory in the Donegal South-West by-election and Labour's Frank McBrearty did not poll as well as some party hacks expected.

While McBrearty greatly increased the party's vote from a low base in the by-election, there is a view that Labour was "spooked" by Sinn Féin's bounce in the polls after Doherty was elected.

Whatever the background to the current battle between Sinn Féin and Labour is, one amusing aspect about it is that both parties blame each other for starting it.

Asked about the spat by Ivan Yates on Newstalk's Breakfast Show last Tuesday, Pat Rabbitte claimed: "Sinn Féin have clearly decided to attack us and they have acquired a high-octane deputy to do it. He was three-and-a-half years in the Seanad and nobody ever heard of him but the coincidence of the Donegal South-West by-election with the intervention from the IMF seems to have given him a higher profile. How long that will last, whether it will last the scrutiny of the general election, I don't know because the platform is simple. The Sinn Féin platform is a plague on all your houses; vote for us, we are against everything.

"The reality is that we don't like this but the IMF and the EU are paying the bills at the moment and you either acknowledge that reality or you find public servants towards the second half of the year not being able to be paid."

Rabbitte claimed that parties could either come up with solutions to the economic crisis or "you come up with high-decibel indignation and [keep] shouting at the ref, which is what Sinn Féin is engaged in at the moment. There is a market out there for that but whether it will survive scrutiny over the period of a general election I don't know."

Similarly, a Labour Party strategist remarked: "The focus during this campaign will be on the main parties – Labour, Fine Gael and Fianna Fáil – so Sinn Féin is just looking for a bit of the action. The real battle between Sinn Féin and Labour is going on in the constituencies. It is no surprise that Roisín Shortall would be attacking Sinn Féin as there is a threat from them in her constituency.

"We are in the middle, between the United Left Alliance and Sinn Féin to our left, and Fine Gael and the right-wing economist independents such as Shane Ross. Our broader battle is with Fine Gael to see who is going to lead the next government. The reality is that Sinn Féin only really has a chance of winning seats in 12 to 15 constituencies at most.

"Sinn Féin is doing what the Labour Party has done on various occasions in the past; it is trying to be relevant. We have lost out in the past where the main focus has been on Fine Gael and Fianna Fáil.

"But nobody is going to let Sinn Féin away with its economic bullshit. People won't ignore Sinn Féin but the main focus on it will come from individual candidates in individual constituencies."

Just as Labour accuses Sinn Féin of "trying to get in on the action", Sinn Féin sources blame Labour for starting the spat.

"There may be a battle but it is one-sided," a Sinn Féin strategist claimed. "If you go back to Gerry Adams' ardfheis speech in 2009, you will see that he made a very significant statement where he called for an alignment of the left. He made a direct appeal to Labour in that speech.

"Prior to that, Sinn Féin's leadership was always wary of the idea of a left alignment. So we cannot understand why Labour is attacking us because strategically we are not going to get the Labour vote.

"We are making the arguments against the EU/IMF bailout and the finance bill to try and attract the lower-middle-class and working-class votes.

"I think that people have been spooked by Pearse Doherty from the day he gave his first speech in the Dáil. Sinn Féin's biggest problem over the last two to three years is that some of our really good spokespeople – Mary Lou McDonald, Pearse Doherty, Padraig MacLochlainn and Toireasa Ferris – were not in the Dáil.

"Caoimhghín [Ó Caoláin] has a grasp of the issues but he is too long-winded, so Pearse's arrival means we have been able to articulate our policies more coherently.

"For the last few years, the Labour Party has tried to sell themselves as offering the 'third way'. Like New Labour in Britain in 1997, who said that they were neither Conservative nor Labour but something different, the Labour Party here are saying that they are neither Fine Gael nor Fianna Fáil. But there is a fundamental contradiction in their strategy as they are looking for centre-ground votes yet trying to appeal to the traditional working-class Labour vote and they cannot follow through on both."

As well as the public row between the two parties, Sinn Féin has found itself at the centre of another storm that has been created by Gerry Adams.

His performances in a series of media interviews last week have rekindled concerns about his grasp of the economic issues in the south.

Adams got trounced in the televised leaders' debate ahead of the 2007 general election. Bill Clinton's famous "it's the economy, stupid" mantra rings louder than ever before in an Irish election context. So Adams' poor performances on RTé's Morning Ireland, BBC Northern Ireland's Newsline and LMFM's Michael Reade Show could unravel the bounce Sinn Féin has enjoyed since Doherty's arrival.

A Sinn Féin insider told the Sunday Tribune: "There is huge loyalty around Adams and people won't even admit that he was that bad. Sinn Féin won't do what Fine Gael has done with Enda Kenny. People are in denial within the party about Adams and they won't hide him away.

"People know he is vague on the economy and he's not good on the specifics but there is a loyalty around him that blinds people to his failings."

And what about the recent surge in support for Sinn Féin? Can it reach the dizzy heights of 15 to 20 Dáil seats?

The party insider pointed out that "the opinion polls never deliver the anticipated seat numbers for Sinn Féin as our vote is spread so thinly across the country. A target of 12 to 15 seats is much more realistic when you break it down."

In a volatile political environment, it is difficult to make seat predictions for any party in Election 2011. But it is safe to predict that the Labour vs Sinn Féin spat will continue.

It may be only a week old but its roots are deep-seated. The Sinn Féin insider remarked: "The generation within Labour that are spitting teeth about us are the old republican left. They don't like to even go into contact with the Shinners."

Battle of the southpaws

Sinn Féin offers an alternative to the consensus for cuts within the three main establishment parties

Martin Ferris on 'The Week in Politics'

It is not in the interests of the country that you would have that kind of rag-bag government

RoisÍn Shortall on 'The Week in Politics'

It's amazing that she is talking about the ultra-left and a rag-bag. Democratic Left were part of a government and Democratic Left now control the Labour Party and that is a reality

Martin Ferris

Sinn Féin are displaying themselves as a party of protest, and I think we are a party of governance

Sean Sherlock on 'the Frontline'

Sinn Féin have clearly decided to attack us and they have acquired a high-octane deputy to do it. He was three-and-a-half years in the Seanad and nobody ever heard of him

Pat Rabbitte on Newstalk's 'Breakfast show'

The generation within Labour that are spitting teeth about us are the old republican left. They don't like to even go into contact with the Shinners

A Sinn Féin insider