Lord Elis-Thomas has been presiding officer since 1999

Dafydd Elis-Thomas, a former Plaid Cymru leader, called for an end to the "ping-pong" over the issue.

Plaid and other opposition parties want candidates to be able to stand in both constituency and regional list seats.

But Welsh Secretary Peter Hain has called the current system "an abuse" of the democratic process.

Lord Elis-Thomas said plans to stop assembly constituency candidates standing on regional "top-up" lists should be accepted because "the argument's been lost".

He has accepted that we've won the argument and I think the argument essentially came down to a democratic principle Welsh Secretary Peter Hain

His call reverses his own personal position, and goes against his own party's policy.

Plaid leader Ieuan Wyn Jones told Radio Cymru that there had been "a number of colourful and provocative statements from Dafydd over the years, but on this matter he's obviously speaking from his position as presiding officer".

However, Mr Jones said while he could see that Lord Elis-Thomas wanted the bill to be passed, "you can't give in to blackmail, because what the Labour Party are saying is that if the House of Lords pull back, perhaps the entire bill will fall".

The Plaid leader called that "constitutional rubbish" and said there was also a human rights issue over preventing a candidate standing on the regional list.

Mid and West Wales Conservative AM Glyn Davies said he was "desperately disappointed" by the presiding officer's comments.

"I understand that Lord Elis-Thomas is very keen to get the Government of Wales Bill on the statute book quickly - but this is political blackmail and partisan skulduggery and the price is too high," said Mr Davies.

Liberal Democrat Montgomeryshire MP Lembit Opik said: "Many of us feel that what the Government is trying to do on this particular issue is to benefit Labour and not to benefit democracy."

I understand that Lord Elis-Thomas is very keen to get the Government of Wales Bill on the statute book quickly - but this is political blackmail and partisan skulduggery and the price is too high Conservative AM Glyn Davies

Earlier this year, the House of Lords defeated the UK Government over the issue, but Labour has pledged to reverse the vote when the bill goes back to the Commons.

Speaking on BBC Wales' political programme Dragon's Eye, Lord Elis-Thomas said carrying on the fight would only delay the new powers for the assembly.

The Meirionnydd Nant Conwy AM said there was a "huge job" to do to get substantial changes to the constitution of Wales in place.

He said: "The important thing for me now is to get the bill on the statute book, to get the next stage of devolution properly set up.

'Common sense'

"There will be slippage if there is last-minute ping-pong play."

Mr Hain said the clause in the Government of Wales Bill was about stopping an "abuse" of the system, which he claimed allowed losers to become winners.

Some AMs have been elected on regional lists despite being defeated in constituencies.

Mr Hain said Lord Elis-Thomas had the "best interest of Wales, devolution and the assembly at heart".

He said: "He didn't particularly favour this policy, but he has accepted that we've won the argument and I think the argument essentially came down to a democratic principle".

"I think he's made a statement that is common sense and is practical, and has the interests of the assembly moving forward rather than fighting, as he puts it, 'old battles'.

But the opposition parties claim the bill is designed to give party advantage to Labour, which does not have any list members.

A report from the select committee on Welsh affairs has endorsed a move to prevent candidates standing in both constituencies and on regional lists.