The party wants to take around €11,000 from Mr Cowen, inset, and Mr Ahern – who get pensions of around €150,000 a year – and give it back to the taxpayer.
The changes would only affect someone with a pension above €75,000.
But McGrath said he wanted proposals that would stand up to legal challenge, and he admitted the pensions were far too high.
"We absolutely accept the pensions are too high and they need to come down,"he said. "The pensions are excessive, there's no question. This is an effort to address that."