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By Adrian Croft

BLACKPOOL, England, Oct 2 (Reuters) - Prime Minister Gordon Brown stoked speculation of an early election on Tuesday by announcing 500 more British troops would come home from Iraq, but analysts say a snap poll would be a big risk for Brown.

Brown's announcement during a surprise visit to Iraq that troop numbers there could fall to 4,500 by year-end could help push aside the unpopular conflict as an issue in voters' minds if he goes ahead with an election next month.

"He is trying to suggest Iraq has been and gone," Strathclyde University politics professor John Curtice said.

Brown's trip overshadowed the Conservatives' annual conference in northwestern England, where party leaders have also moved into campaign mode, announcing voter-pleasing tax cuts and singling out Europe as an election battleground.

The opposition Conservatives criticised Brown's Iraq visit as a "pre-election photo opportunity" and questioned its timing.

Former Conservative Prime Minister John Major urged Brown to end the "feverish and foolish speculation" about an early poll.

"He's letting the speculation run riot ... It is clearly an attempt at the destabilisation of the opposition parties," Major told the BBC.

The ruling Labour Party's opinion poll lead of up to 11 points makes it tempting for Brown to call a snap election, two and a half years before he has to, in the hope of inflicting a fourth consecutive general election defeat on the Conservatives.

Media commentators suggest Brown could announce a November election when parliament returns next week.

But it would be very risky.

"I think it would be a mistake," said Warwick University politics professor Wyn Grant. "An election now might be seen as opportunistic."

Anthony King, professor of government at Essex University, said an election now held considerable risks for Brown.

"At worst Labour could lose. More probably there would be a very low turnout, Labour's majority would not be increased, the prime minister's authority would be severely damaged," he said.

If Brown lost, he would go down as one of the shortest-serving British prime ministers in history.

CONSERVATIVES EXPECT ELECTION

Conservative leader David Cameron said there was a more than 50 percent chance Brown would call an election in the next month. "I expect there to be an election, and if there is an election, then I think we can win it," he told the BBC.

Brown's decision could depend on voters' reaction to the Conservatives' conference this week. If Brown decided not to call a poll, the Conservatives would portray that as Brown backing down and a victory for them.

"We've got to have a really good conference. Then he will be concerned and he'll say: "No, I won't bother'," said Les Topham, 69-year-old leader of Stratford-on-Avon District Council, attending the Conservative conference.

But Margaret Jackson, a delegate from Cheshire in northwestern England, said she did not think the Conservatives would get back into power unless there was an economic downturn.

"Nobody feels the need for change," she said. "I don't think David Cameron is putting us in really the right direction."

Since taking over from Tony Blair in June, Brown has distanced himself from unpopular or controversial Blair policies such as the Iraq war and plans to open super-casinos.

Cameron's poll numbers have slumped due to a series of public relations gaffes and resistance from right-wingers to his attempts to drag the party towards the centre.

Further arguments for Brown to call an election now are the global credit crunch and tight public finances which suggest next year may bring more difficult economic times.

But analysts caution that opinion polls are fickle and voters could easily swing against Brown during an intense three-week campaign. Holding a poll in November, when it gets dark early, would also depress voter turnout.

The Conservatives appealed for the middle-class vote on Monday by pledging to sharply raise the threshold for paying inheritance tax and exempt most first-time home buyers from a transaction tax.

Grant said this was part of a Conservative strategy aimed at winning marginal seats in wealthy southern England.

On Tuesday, Conservative foreign affairs spokesman William Hague also pledged to turn the demand for a referendum on a new EU treaty into a key election battleground.

Attacking Brown's refusal to permit a referendum, Hague said a Conservative government "elected this autumn" would not only hold a referendum but change the law to oblige future governments to consult people on treaties that transferred powers to Europe. (Additional reporting by Tim Castle and Kate Kelland)

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