Plaid Cymru honorary president Dafydd Wigley has criticised the Welsh Assembly Government coalition deal his party struck with Labour.
Dafydd Wigley says there is little chance of winning a referendum
At the National Eisteddfod, the former party leader said the One Wales document was compiled too quickly.
He also said almost half the policies in the document would need more funding, which had not been secured.
He also argued that there was little chance of winning a referendum on the assembly gaining law-making powers.
The One Wales agreement was struck in July, two months after Labour failed to win an overall majority at the assembly election and sought a deal with Plaid.
It is the foundation upon which the coalition was built and sets out objectives over the next four years.
It includes an agreement on a referendum on full law-making assembly powers "as soon as practicable" in 2011 or before.
The parties also agreed "in good faith to campaign for a successful outcome" to a referendum.
But in his speech at Mold, Flintshire, Mr Wigley presented a detailed critique of the political events leading up to the coalition deal with Labour and the prospects for it to succeed.
Mr Wigley said he believed the chance of a yes vote in a referendum on law-making powers for the assembly was a remote possibility, indicated by Labour's May election performance.
Labour's share of the vote then was 32%, the lowest since 1918.
He also said he believed here was little point in conducting a referendum.
Mr Wigley, who tried but failed to be returned to the assembly in May, expressed concern about the opposition of some Labour MPs to the One Wales document and the effect this could have on any referendum campaign.
It would put back the campaign to convert the assembly into a full law-making body by a generation, he said.
Mr Wigley argued that of 217 specific policies set out in the document, 102 of them would need additional resources for which funding has not been secured.
The deal should not have been struck without this money, he said, and if the coalition document were delivered, it would necessitate cutbacks in other areas.
However, Mr Wigley argued the One Wales document would deliver and that he would be challenging his party to work as an effective partner in government.