Fianna Fáil and Labour are negotiating a deal to preclude Fine Gael from retaining its traditional hold on the chairmanship of the powerful Dáil Public Accounts Committee (PAC).
The two parties are engaged in private talks on the possible election of Labour TD Mr Pat Rabbitte to the chairmanship of the most prestigious committee in the Dáil, The Irish Times has learned.
The move is the first sign of a shift in the opposition balance of power following Fine Gael's devastating loss of 23 seats in the General Election.
If Mr Rabbitte is elected chairman of PAC, it will be the first time since the committee was established that the post has not been held by the main party in opposition.
There is now only a 10-seat gap between Fine Gael and Labour, with Fine Gael holding 31 seats and Labour 21.
In the last Dáil Fine Gael held 54 seats and Labour 21.
Fine Gael has already chosen its Sligo-Leitrim TD, Mr John Perry, as its nominee for committee chairman.
The committee is not due to be formally established until September, but all parties have already selected their nominees.
Senior Labour party figures approached Fianna Fáil in recent weeks to sound it out about supporting Mr Rabbitte for the key position.
Mr Rabbitte could not be contacted for comment last night.
However, a Labour Party spokesman told The Irish Times: "Given the new post-election position, Fine Gael no longer occupies a major position within the opposition.
"Obviously this is something we will be looking at in the context of the committees."