Gordon Brown receives striking new polling evidence today that he would comfortably win a general election this autumn.

A special Populus survey for The Times gives Labour a double-digit lead, meaning that the Conservatives will arrive in Blackpool tomorrow for their make-or-break conference more convinced than ever that an election is imminent. A second poll, carried out by YouGov for The Daily Telegraph, shows a similar lead. The Prime Minister will meet allies this weekend to consider his options.

But Mr Brown suffered a setback last night when one of his newest Cabinet ministers was accused of helping to fake a photograph.

James Purnell, the 37-year-old Culture Secretary, who lectured the media recently about the importance of trust, was pictured in a doctored photograph that suggested, falsely, that he had attended an event with other MPs to promote a hospital building programme.

In fact, the NHS trust said that he had arrived late and agreed to pose for a photograph in the same spot. It was then merged into a picture of the other MPs taken earlier and placed on the trust’s website.

The Conservatives called on Mr Purnell to resign last night. Jeremy Hunt, the Shadow Culture Secretary said that his position looked “completely untenable”. Mr Purnell had warned the media about “forfeiting public trust” with recent scandals over faked footage and competitions.

The MP last night said that there had been a “misunderstanding” over the picture and that the hospital trust had acted in good faith.

“I thought it would be done in a way that made clear that I had arrived later and the picture was a slightly different one,” Mr Purnell said. I didn’t see this picture and, if I had done, I wouldn’t have approved it going out.”

The Populus poll, undertaken on Wednesday and Thursday as the Labour conference was ending, put the party on 41 per cent, against 31 per cent for the Conservatives and 17 per cent for the Liberal Democrats.

The last Populus poll was done at the beginning of the month after David Cameron’s counter-attack had succeeded in narrowing the gap between the main parties to one point. But Labour has risen by four points since then, and the Tories have dropped by five.

All but one poll this month has put Labour on at least 39 per cent and the average ratings for the main parties in September would, if repeated in a general election, give Mr Brown an increased Commons majority of more than 100, with the Tories making no progess on their showing in 2005.

The lead published in The Daily Telegraph today is even larger than that in the Populus poll, with the 11-point advantage the highest in any recent survey. The YouGov poll, in which Mr Brown also outstripped Mr Cameron in his personal ratings, gave Labour 43 per cent, the Conservatives 32 per cent and the Liberal Democrats 15 per cent.

These figures may have been boosted by the publicity surrounding the Labour conference in Bournemouth but, despite volatility from poll to poll, the underlying trends are stable and favourable to Mr Brown.

The Prime Minister and his allies — most of whom now want him to go early — will not take a formal decision this weekend, knowing that it would leak out immediately if they did. Instead, Mr Brown is expected to hold another council of war later in the week and probably once again next weekend.

He is reluctant to call an election during the Conservative conference but, if he wanted an election as early as October 25, he would have to call it on Tuesday. It is more likely that he will wait until the Commons returns on Monday week and make an early statement on British forces in Iraq.

An election on November 1 would have to be called by October 9 and an election on November 8 would have to be called by October 16.

The Conservative leadership will have no choice this week but to call on Mr Brown to hold an election, even though many Shadow ministers are deeply worried at the prospect.

There are growing signs that David Cameron and his team are to give more emphasis than expected to core Tory policies in a bid to bolster traditionalists in the run-up to the battle.

There was something of a boost for the Tories in Thursday’s byelection results, where the party gained a Sunderland seat from Labour and achieved favourable swings, though no wins, in wards in Corby and Portsmouth. However with several other swings to Labour, the council results alone are unlikely to dissuade Mr Brown from calling an early election.

opulus interviewed a random sample of 948 adults aged over 18 by telephone between September 26 and 27. For more details go to www.populus.co.uk

Explore UK News

• Crime News

• Education News

• Health News

• Scotland News

Times Recommends

• Milk: do we need a dairy godmother?
• DIY: the women doing it for themselves
• First double portrait of Princes unveiled