On the eve of Labour's final vote on a proposed coalition with Plaid Cymru, two senior MPs have urged their party to reject the deal.
Paul Murphy said the Labour party was divided on the issue
Paul Murphy, the Torfaen MP and former Welsh secretary, and former Wales office minister Don Touhig, who represents Islwyn, have spoken out.
Mr Murphy said Labour should continue in minority government, and Mr Touhig said power-sharing was the wrong step.
Labour will vote on the coalition at a special conference on Friday.
Mr Murphy told BBC Wales' Dragon's Eye he thought the coalition would be approved, but did not think it was in the best interests of the party.
He said he believed many Welsh Labour MPs and party members did not support the deal and that a Labour minority government in the assembly "could last three years".
"A coalition with the biggest opposition party, whose ideals and values do not sit comfortably with many of our own, should not be entered into lightly," he said.
Mr Murphy said he understood the dilemma faced by First Minister Rhodri Morgan, but maintained he had a right to express a view about the content of the One Wales document which forms the basis of the coalition proposal.
"The party is certainly divided on the issue and we will have to see when we get that vote on Friday," he said.
"There is no point in pretending the party is in any way united on this issue. There is considerable discomfort right across Wales about this.
"In the end, the party will decide and there is nothing wrong in members of parliament, members of the assembly, members of trade unions [and] members of constituency parties disagreeing on issues because that's what they call debate."
Rhodri Morgan and Ieuan Wyn Jones agreed the One Wales deal
Mr Touhig, meanwhile, said it was time to "be blunt".
"We are a great family the Labour Party and we have this conference tomorrow, and I think we'll hear a lot of home truths on both sides of the argument. I think this is crucial for Wales and crucial for the Labour party.
"The people of Wales did not vote for this in the assembly elections, they voted for a majority Labour administration. We got most of the votes and we should carry on in power."
A number of Labour politicians have already broken ranks over proposed coalition.
On Wednesday, Torfaen's Lynne Neagle was first to speak publicly against the "One Wales" deal, and she was later backed by colleagues Karen Sinclair, Ann Jones and Irene James.
Labour MP Kim Howells is also said to have warned it would help "nationalists to the gates of independence."
The One Wales agreement has received backing from both Labour and Plaid AMs and Labour's Welsh executive, as well as Plaid's national executive.
But an "overwhelming majority" of Welsh Labour MPs are said to have "serious concerns".
Labour failed to win a majority in the 3 May election and has been running a minority administration at Cardiff Bay.
But a historic power-sharing deal with Plaid Cymru was agreed in principle by First Minister Rhodri Morgan and Plaid leader Ieuan Wyn Jones.
Plaid abandoned the idea of a "rainbow alliance" with fellow opposition parties, the Liberal Democrats and Conservatives, in favour of the move.
Tory leader Nick Bourne has said that creating an anti-Labour government in Cardiff Bay was "more urgent than ever before" and it would be "foolish" to cast aside a rainbow deal into which "much hard work, time and thought" had been dedicated.
Plaid Cymru will follow's Labour discussions on the alliance with their own special conference on Saturday.