FIANNA Fail and the Progressive, Democrats moved last night to play down suggestions of a rift in their approach to monetary union.

Mr Des O'Malley, the Progressive Democrats spokesman on foreign affairs, told RTE yesterday that one of the most momentous decisions in the history of the State was being made with the minimum of political debate.

This line echoes party leader, Ms Mary Harney, who said in an interview with The Irish Times last week that it was "unrealistic" to expect, Ireland to survive in a German-based union, if Britain was excluded.

She also called for a comprehensive review of the possible repercussions for the Irish economy, if Britain goes it alone.

But Mr Ahern, the Fianna Fail leader, had made it abundantly clear on numerous occasions that he was fully behind monetary union, a spokesman said yesterday.

Mr Ahern has no doubt that Ireland should enter monetary union, even if Britain stays out.

"It has to be good," he said in an interview with this newspaper yesterday.

Going into the single currency would lower transaction costs for business and maintain lower interest rates. Remaining outside could deter tourism and inward investment.

A spokesman for Mr Ahern dismissed the differences between the parties, stating: "If we all had the same policies, we should all be in the same party."

A spokesman for the PDs also dismissed the differences as merely a matter of emphasis.

But the Minister of State for Commerce, Mr Pat Rabbitte, said the Fianna Fail-PD coalition was "disintegrating" before our eyes.

Speaking at Dublin City University, Mr Rabbitte, said post-Budget rebellion among Fianna Fail backbenchers was widespread.

"A FF/PD alliance will not have enough support to form a Government at the end of the year," he said.