Gordon Brown has chosen the West Midlands to launch the first stage of Labour’s general election campaign and reveal the key themes of his manifesto will be jobs, the economy and cutting crime.

The Labour leader will be in the region on Saturday for a high profile event where he will also unveil the party’s election slogan.

Although he will not formally announce a general election, the event will be seen as the unofficial launch of the election campaign.

The West Midlands was chosen for the event because of the high number of key marginal seats where Labour is trying to fight off David Cameron’s Conservative Party, such as Birmingham Edgbaston, Stafford, Redditch, Wolverhampton South West, Dudley South, Nuneaton and Worcester.

The themes chosen for the campaign will mark a major break with Labour’s electoral strategy since 1992, when the party has concentrated on offering higher public spending in public services such as schools and hospitals, in contrast to Conservative “cuts”.

They suggest that Business Secretary Peter Mandelson has won his battle to convince Mr Brown that Labour cannot hope to win the next election by promising to spend more than the Tories.

This has put him on collision course with Cabinet rivals such as Ed Balls, the Schools Secretary, who was reported to be pushing for a more traditional election campaign.

Lord Mandelson will also be present at the event, as well as Alistair Darling, the Chancellor, Yvette Cooper, the Work and Pensions Secretary, and Alan Johnson, the Home Secretary.

A full Labour manifesto will be launched at a later date.

Mr Brown is also expected to a call on “progressives to come together to defend and protect the values they cherish” and suggest that Labour must be at the centre “of a wider movement”.

Party officials denied this was an attempt to woo Liberal Democrats in the face of a difficult battle to stay in office. Some commentators believe the General Election, still expected on May 6, could result in a hung Parliament, so that Mr Brown would need Lib Dem support to remain in Downing Street.

Saturday’s event is also seen as a substitute for Labour’s annual spring conference, which has cancelled this year in order to save money in preparation for the campaign.

A Labour source said: “It is a pre-election platform to set out some of the ideas we believe the election should be about.”