NI parties are setting out their positions on a Westminster coalition as formal talks between Labour and the Lib Dems are due to begin.
The DUP said it was not ideologically opposed to a Lib-Lab agreement but would vote in the interests of NI.
The SDLP said it would prefer an agreement between Labour and the Liberal Democrats.
Gordon Brown, who is to step down as Labour leader, said talks with the Lib Dems were in the "national interest".
Role
BBC Northern Ireland political editor Mark Devenport explained the potential role for Northern Ireland MPs in a coalition.
"If Labour did a deal with the Liberal Democrats, they would have a parliamentary strength of 315," he said.
"That is 11 short of the formal margin for a Commons majority of 326 but the absence of the five Sinn Fein MPs lowers the effective margin to 324.
"If all the 13 remaining Northern Ireland politicians decided to back a Labour and Liberal Democrat government, that would take a Labour and Liberal Democrat government to 328, enough for a very small majority."
DUP deputy leader Nigel Dodds said that his party was not ideologically opposed to a deal between Labour and the Liberal Democrats.
"We would only be prepared to look at things on a case by case basis," he said.
"We have always said that we would only do so on the basis of Northern Ireland’s interests being protected in terms of the block grant, the economy and so forth."
Alasdair McDonnell of the SDLP said his party would prefer a Lib-Lab deal "because of the horrific memories of the Conservatives under Thatcher".
He added that his party believed David Cameron was planning "slash and burn" cuts.
Block grant
Meanwhile, Stormont party leaders have discussed reaching a common position on the NI block grant as their MPs votes could be vital in forming a new government.
A meeting took place on Monday, attended by the Sinn Fein president Gerry Adams, the SDLP leader Margaret Ritchie and David Ford of Alliance.
Both unionist leaders sent their apologies.
It is understood the matter is likely to be discussed at a meeting of the Stormont executive on Thursday.
During First Minister’s Questions in the Assembly on Monday, the new Alliance MP for East Belfast, Naomi Long, again suggested that the 13 MPs intending to take their seats should seek common ground on defending Northern Ireland’s interests.
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