David Cameron will campaign against vote change

Prime Minister David Cameron will campaign for a "no" vote in a referendum on electoral reform expected to be held next year, Downing Street confirmed today.

The Tory leader is "not in favour" of switching from first-past-the-post to the alternative vote (AV) system for electing MPs and will make that clear during the campaign, his spokesman said.

That will put him at odds with Deputy PM Nick Clegg, whose Liberal Democrat party secured the promise of a national vote as a key condition to forming the coalition Government.

Mr Clegg is expected to announce the date of the referendum next week following approval by the Cabinet - with May 5 next year widely expected to be the chosen date.

Details will be included in a Government Bill - which will also feature Tory proposals to re-draw boundaries to ensure a more equal number of voters in each.

Tory MPs will be whipped to back the Bill, but bitter opposition to electoral reform among many backbenchers may provoke a rebellion against Mr Cameron.

The referendum itself is bound to put the coalition under strain and there had been suggestions Mr Cameron could step back in a bid to avoid provoking tensions.

But his spokesman told reporters: "He will be campaigning against AV.

"I can't predict precisely how the campaign will unfold but clearly he is going to be asked his views during that campaign and he will make them clear.

"His view is that he is not in favour of it."

Mr Cameron defended the first-past-the-post system during the general election campaign, warning that proportional representation would lead to unstable and damaging coalition governments.

Downing Street refused to confirm reports that the referendum would be held on May 5 next year - to coincide with local polls in England and Scottish Parliament and Welsh Assembly elections.

"You will have to wait for the announcement because obviously that should be made to Parliament first," the spokesman said.