The race for the Ealing Southall seat in west London will be the first electoral test of Gordon Brown’s premiership.

A joint statement was issued by the five defectors, Gurcharan Singh, Manjit Singh, Maninder Kaur Keith, Jarnail Singh Jandu and Jagdish Gupta.

They said: “It has become increasingly obvious as this by-election campaign has progressed that the Conservative candidate Tony Lit is the best person to represent Ealing Southall as our next MP.

“We wanted to provide him with our backing and joining the Conservative Party sends the clearest possible message.”

Many Sikhs are disappointed Labour has not chosen a “visible” Sikh for the safe seat. The election was caused by the death of Labour’s Piara Khabra. Tories finished third behind the Lib Dems in the 2005 general election.

We wanted to provide him with our backing and joining the Conservative Party sends the clearest possible message

Both major parties are giving the Ealing Southall by-election high priority. Justice Secretary and Lord Chancellor Jack Straw and Tory leader David Cameron yesterday appeared on the steps of Ealing Town Hall within half an hour of each other.

Voting takes place on Thursday next week – the same day as in Tony Blair’s Sedgefield seat.