Kennedy returns to lure votes

The contest follows the death last month of Labour MP Rachel Squire, who won a majority of more than 11,500 in last year's General Election.

The Lib Dems overtook the SNP to come second last May but their lead over the Nationalists is narrow and they have also had the distraction of the party leadership contest.

Activists hope Mr Kennedy's personal popularity can boost the campaign of Willie Rennie, who insists the contest is a two-horse race with Labour's candidate, the MEP Catherine Stihler.

Mr Rennie described Mr Kennedy as "a great campaigner", adding: "He is very popular and his visit will give us the boost we need to overtake Labour in the last few days of the campaign."

However the Tories, whose candidate is Carrie Ruxton, have the Lib Dems in their sights and hope to improve their fourth place position.

Speaking ahead of his visit, Mr Cameron said: "We are the party committed to decentralisation and defending civil liberties and there is now a new home for the Liberal Democrat voters and those who want to see a change of government at the next election."

Mr Brown, who is the neighbouring MP, will tour a subsea cable manufacturing plant in Rosyth where 40 new jobs are planned.

"These are the kind of high-quality jobs which we need to grow the economy in Fife," the Chancellor said ahead of his visit.

SNP leader Alex Salmond, who is also in the constituency with candidate Douglas Chapman, claimed the Lib Dems have "lost their way" and dismissed the Tories as "rank outsiders".

Press Association