A Labour Party spokesman confirmed that the pop queen had wished Labour leader Tony Blair good luck in the 7 June Election.
The signed goodwill message from Spears, 19, was received by Tony Blair's press secretary, Alastair Campbell.
Campbell, 43, took his six-year old daughter to see Spears perform at London's Wembley Stadium last year, and later attended a post-concert party for the singer at London's Planet Hollywood.
The Daily Star reported that the signed photo containing the goodwill message is now on the wall at Labour's headquarters in Millbank.
Despite their protestations that celebrities do not matter, political parties rarely refuse support from the stars.
Labour has so far benefited from the endorsement of actors Maureen Lipman and Kevin Whately - who provided the voiceover for the Geri Halliwell broadcast.
Paralympic athlete Tanni Grey-Thompson also made a public declaration of support for Labour in the same broadcast.
A Conservative Party spokeswoman told BBC News Online that the party had no plans to enlist the help of celebrity figures, though the party is using campaign music composed by Wombles creator Mike Batt.
And celebrities Sir Tim Rice, Patti Boulaye, Jim Davidson, Anthony Worral-Thomson, Anthony Andrews and Dana have all recently been associated with Conservative party fund-raising.
Former television film pundit Barry Norman is likely to speak at a London rally for the Liberal Democrats during the campaign.