British Finance minister Gordon Brown said today that parliament and not the prime minister should have the final say on whether Britain goes to war.
In an interview with the Daily Telegraphnewspaper the chancellor of the exchequer said the precedent set two years ago in allowing members of parliament to vote before the Iraq war should remain.
At present the prime minister can use the royal prerogative to launch military action without parliamentary assent.
Mr Brown, widely viewed as Prime Minister Tony Blair's rival for power and also his probable successor, made his comments after days when the lead-up to the Iraq war dominated the campaign for a May 5 parliamentary election.
"Now that there has been a vote on these issues so clearly and in such controversial circumstances, I think it is unlikely that except in the most exceptional circumstances a government would choose not to have a vote in parliament," Mr Brown said.
"I think that Tony Blair would join me in saying that, having put this decision to parliament, people would expect these kinds of decisions to go before parliament."
The deeply unpopular Iraq war remains Blair's Achilles Heel.
Opponents have said the prime minister misled parliament ahead of a 2003 parliamentary vote which backed the US-led invasion.
On Wednesday Mr Blair's critics jumped on leaked advice from the government's top lawyer which showed the attorney general harboured some doubts about the legality of the conflict.
Mr Blair countered on Thursday by publishing Mr Goldsmith's full advice which showed that while the lawyer had some reservations about the legal basis for war there was "a reasonable case" based on UN resolutions.
Although the Mr Goldsmith leak ruined Labour's efforts to focus the campaign on domestic issues like the economy and health most analysts say the issue of Iraq is unlikely to sway many voters at this late stage.
All polls point to Mr Blair winning a third term.