Plaid Cymru has ruled out entering a coalition government with any other party in the Welsh assembly.
President Dafydd Iwan opposes coalition talks
Plaid's leaders have said it will not even discuss a deal with another party before the assembly elections in 2007.
Labour's recent loss of its assembly majority has led to talk of a coalition involving Plaid, the Conservatives and the Liberal Democrats.
Plaid members who backed the idea included ex-leader Dafydd Wigley and former AM and MP Cynog Dafis.
But the suggestion was heavily defeated at a meeting of Plaid's national council, the party's decision-making body.
President Dafydd Iwan said Plaid would not "dilute its policies at the behest of the Conservative party or any other party".
Dafydd Wigley could stand for election to the assembly
"Coalition is not on the party's agenda at this stage," he added.
"We are not seeking to form a coalition with anybody, we are not talking to any other parties about coalitions, and we are not going into the next election with any aim other than to win enough seats to form the next government.
But Mr Iwan said the position could be reviewed after the 2007 election.
"If, after any assembly election, no party has a clear majority, then clearly all the parties would have to look at alternative arrangements," he said.
Labour lost its assembly majority earlier this year when AM Peter Law left to stand against the party's official candidate in the general election.
Mr Wigley, who supported the idea of a coalition, retired as constituency AM for Caernarfon in 2003, but has recently been increasingly involved in frontline politics again.
Last month, Mr Wigley and Mr Dafis announced the creation of a lobby group, called Dewis (Choice), which advocated linking up with other opposition parties.
When Dewis was launched, Mr Iwan described the idea as a potentially "huge political mistake".
On Sunday, Mr Wigley indicated he may be willing to consider a return to politics, and had not ruled out standing at the next Welsh assembly election in 2007.
Mr Wigley, who also served as MP for Caernarfon for 27 years, said he would be "duty bound" to consider a return to the assembly if the party wished it.