Fine Gael and the Labour Party have said they believe close co-operation between the two parties is the best way to offer an alternative to the Government's "failed" policies.
The parties were formally announcing an election pact for the March 11th by-elections to fill the vacant Dáil seats in Meath and Kildare North.
Announcing the transfer pact in Dublin, the parties insisted the pact was not a 'dry run' for a future general election, but was instead designed to maximise votes for the two Opposition parties in the ballot next month.
The party leaders also dismissed a Fianna Fáil by-election candidate's contention today that the pact was 'cynical' because the two parties did not agree on a number of issues, including the controversial route for the proposed M3 motorway in Meath.
The Fine Gael leader Mr Enda Kenny, said the parties agreed on a "whole range of issues" where the Government had failed to deliver in Meath and Kildare.
He cited childcare, schooling, infrastructure, commuting and "other social pressures" on families, who he said were "completely frustrated".
Both leaders said they had procedures to follow within their parties in order to confirm policy positions. Mr Kenny said the current pact would build on last year's transfer agreement during the local and European Parliament elections. He said the Meath and North Kildare constitutencies were not two he would have chosen in which to win by-elections because of the traditional [Fianna Fáil] voting strength and that was why it was necessary to maximise the transfers.
The Labour Party leader, Mr Pat Rabbitte, said it was his intention that the people be "offered a choice" at the next general election, but he also had procedures to go through and the issues would be debated at the party's annual conference in Tralee, Co Kerry, at the end of May.
He said a general election was "a long way away in all probability" and there was plenty of time to discuss in what terms an alternative would be offered to the present Government.
Mr Kenny accused the Government of a "growing arrogance" and of being in such a "comfort zone" that it had indicated to the electorate in Kildare that it would be "wrong" not to have a Fianna Fáil TD.
He said said the Fianna Fail party had a Minister for Finance in the constitutency but had "shafted" Mr Charlie McCreevy following the Government "sit-in" at Inchydoney last year.
Fianna Fáil's by-election candidate in Kildare North, Ms Áine Brady, dismissed the voting pact "cynical" and said it had "nothing to offer the people" of the constituency.
"This arrangement cannot be taken seriously when the parties are so divided on basic issues. Take the whole equine industry which is an issue of major interest to the people of Kildare, as so many jobs and livelihoods are connected to it." Ms Brady said.
"The Labour party - as has been made clear by its party leader on a number of occasions - is fundamentally opposed to the special tax status of the industry. Yet just last week the Fine Gael candidate was reported as calling for the retention of the tax exemption. Nothing could illustrate more the basic divide between the parties."