Conservatives have held consistent poll leads for the next election
A Conservative general election win would raise questions about the system of gradually transferring powers to the Welsh assembly, a senior AM has warned.
Presiding Officer Dafydd Elis Thomas said Tory MPs could reject bids because they oppose the policy being proposed.
But the Conservative Party said it wanted to improve the process before it put "unsustainable pressures" on Cardiff-London relations.
Tory MP David Jones also said such "stirring the pot" would not help.
Lord Elis Thomas told an audience at a Law Society event at the National Eisteddfod in Bala, Gwynedd, that the system by which the assembly draws down new powers from Westminster "has worked to a certain extent" but is far too lengthy and complicated.
If the assembly needs new powers to pass a law, on matters such as education, agriculture or health for example, it needs Parliament to pass a Legislative Competence Order (LCO) granting it the powers to legislate.
It is this process, introduced two years ago, which Lord Elis Thomas believes is taking too long.
He argued MPs should not be examining bids for powers in so much detail unless "constitutional questions" were involved.
He also warned that a general election could scupper bids already in the pipeline, including a much-delayed request for powers to legislate on the Welsh language.
He said: "With a parliamentary general election approaching, there is an increasing risk that important orders which have not completed the process when an election is called will therefore fall, and will need to start the process again following the election."
Lord Elis Thomas also raised concerns about how the system might work with a Conservative majority at Westminster.
"Of course, the election of a Conservative majority in the House of Commons would raise questions regarding the sustainability of the process," he said.
"What if a Welsh affairs committee [which scrutinises LCOs] with a majority of members from that party decided to recommend rejecting a Legislative Competence Order because the policy proposed to be implemented under the proposed competence was not to the liking of those members?"
But he suggested a move to hold a referendum in Wales on giving the assembly full law-making powers all at once, rather than piecemeal, would gain momentum if there was Conservative opposition at Westminster to the bids for powers.
A Welsh Conservative spokesman said: "We have repeatedly stated that we want the National Assembly to work in the interests of everyone in Wales and that devolution is here to stay.
"However we do have concerns - shared by many people - about the current settlement, devised by Labour, which is a recipe for confusion and conflict.
"As a party we've been looking at ways of improving the legislative process and ending the logjam before it places unsustainable pressures on the relationship between Cardiff and London."
David Jones, Conservative MP for Clwyd West, wrote on micro-blogging site Twitter: "Dafydd El's insistence on stirring the pot is doing no good for relations between Parliament and the assembly."
Mr Jones also wrote on his blog that every report on LCOs by the Welsh affairs select committee had been delivered unanimously, and it included three Tory MPs, as well as one Plaid.
"There is consequently no obvious basis whatever for Lord Elis-Thomas's typically inflammatory assertion," wrote Mr Jones.
"Lord Elis-Thomas's overtly and provocatively political stance sits oddly with what ought to be his neutral role as presiding officer.
"I wonder how he would react if [House of Commons] Speaker Bercow were to start criticising or second-guessing the workings of an assembly committee. No doubt, in his usual moderate and measured manner."