LONDON — Prime Minister Brown is preparing to fight a general election as soon as October, ruling Labour Party officials said.

“The Labour Party needs to be ready for a general election whenever the prime minister is ready to call it,” Martin Salter, a Labour member of Parliament and vice chairman of the party, said in a telephone interview yesterday.

Philip Gould, a Labour lawmaker in the upper House of Lords who has served the party as a polling analyst, urged Mr. Brown to pursue a “shock attack strategy,” according to a leaked memo published by the Daily Mirror yesterday. October is the earliest an election could be held.

Labour has established a consistent lead over the Conservative Party since Mr. Brown succeeded Prime Minister Blair on June 27, prompting speculation he may call an election well before the deadline of June 2010. Talk of an early vote has placed Conservative leader David Cameron under fire from some members of his party who say he lacks the substance to take on Mr. Brown.

Mr. Cameron, who has focused on softening the image of the party after three election defeats to Labour in a decade, is under pressure to commit the party to more policies that appeal to traditional Conservative supporters, such as lower taxes.

The Conservatives failed to make headway in two by-elections last month, and Mr. Cameron was criticized for visiting Rwanda when some of his constituents had been forced from their homes by Britain’s worst floods in 60 years. The party has trailed behind Labour in 10 polls since Mr. Brown took over, having led for most of the previous 15 months.

By contrast, Mr. Brown in his first month in office has won praise for his handling of the floods and failed car bombings in London and Glasgow.

Cabinet Office minister Ed Miliband played down speculation of an early election, saying the memo may have been written two years ago and that he had no recollection of the document being discussed.

“We have been in for five weeks and it is important not to get carried away,” Miliband, who has been charged with writing Labour’s election manifesto, told BBC Radio 4’s ‘World at One’ program.

“I remain convinced that Gordon Brown won’t go to the country this year, since the strong showing in the opinions polls can’t be sustained enough in the short time available before a decision needs to be made,” said Anthony Wells, a polling analyst at YouGov Plc. “However, there must come a point when the sheer size of his lead outweighs that.” In the most recent poll published at the end of July, 39% of voters said they would back Labour if an election were held now, up 2 points in a month and 6 points ahead of the Conservatives, according to Populus Ltd. No margin of error was given.

“We have to have a strategy or audacious advance,” Mr. Gould writes in the memo, according to the Mirror. “The best way of achieving this is to hold an early election after a short period of intense and compelling activity.”

Mr. Gould says one of the difficulties facing Mr. Brown is following Mr. Blair, who was seen as a “charismatic” leader. He says it would be unwise of Mr. Brown to try to emulate his predecessor.

Mr. Brown, who was finance minister for a decade, has signaled a clean break with the Blair era, with promises to overhaul the constitution, impose harsher penalties for cannabis possession and to review a plan to build super-casinos.