The Liberal Democrats are preparing for a possible snap election within a year.

According to a strategy document drawn up by campaigns chief Ed Davey, the party is looking at ways to target Gordon Brown and David Cameron's weaknesses.

And party leader Sir Menzies Campbell said he had asked chief executive Lord Rennard to start preparing an election manifesto.

The Lib Dems believe it is "a racing certainty" that Gordon Brown will have succeeded Tony Blair as Labour leader and prime minister by next May or June.

And Sir Menzies, speaking to Sky News on Thursday, said: "I think there's a chance that Gordon Brown could be tempted to go for an election in as little as 12 months.

"I think we've got to be ready for that."

A two-day meeting of the Lib Dem front bench is starting today in Henley-on-Thames.

The document says: "The focus of this meeting should be to ensure all shadow cabinet ministers turn their fire on Brown's legacy as chancellor."

It suggests Brown has a "100 day strategy" to "establish a Brownite feel to Labour initiatives", and says he is open to attack over public services, Iraq and his perceived lack of liberality.

And it suggests that the Conservative leader is increasingly viewed with scepticism by the public and the media, saying: "Cameron's star is fading."