Fianna Fáil is claiming that election promises made by the proposed alternative coalition would cost an unrealistic amount of money to implement.
The party says it has examined the Fine Gael and Labour policies and the bill runs to at least €14bn per year.
It says this amounts to €10,000 for every individual taxpayer in the country.
The claim appears designed to undermine the opposition parties as they prepare to launch their joint economic policies this morning.
Fine Gael TD Fergus O'Dowd, however, says the Fianna Fáil figures are wrong and are nothing but propaganda from a desperate party.
He says Fianna Fáil has wasted hundreds of millions of euros worth of taxpayers' money in recent years.