Pro-AV campaign surges to 10-point lead

Campaigners demanding a change in the voting system for Westminster elections have secured a 10-point lead over opponents, as peers are threatened with losing their holiday if they derail the referendum planned for 5 May.

An exclusive poll for The Independent on Sunday reveals 40 per cent of people surveyed now back a switch to the alternative vote (AV), while 30 per cent want to keep first-past-the-post (FPTP). The four-point increase in support for the yes campaign since January comes direct from those who last month responded "don't know", suggesting that as the campaigns step up a gear public support for reform is hardening.

On Friday, David Cameron and Nick Clegg are due to go head to head in the battle over electoral reform, giving speeches on the same day setting out conflicting views.

In a high-wire demonstration of the opposing policies at the top of the coalition, the Prime Minister will spell out his arguments for keeping FPTP. But, within hours, his deputy will seek to demolish his boss's position, advocating a switch to AV.

Last night, Mr Clegg told this paper: "The coalition government is open about our disagreements. Electoral reform is one of them. The Government is clear that it is the people who should choose the way they elect those who represent them. Both sides can make their case, but it is for the public to decide."

The Deputy PM will enjoy the rare sensation of being back on the side of public opinion. However, the detail of the IoS poll on electoral reform will also make awkward reading for the party leaders. One in 10 Lib Dems (11 per cent) say they will vote no to AV, while 28 per cent of Tories will vote yes. Ed Miliband, who has faced criticism from Labour ranks for backing AV, will take heart from his stance being supported by 40 per cent of those who say they will vote Labour.

Paul Sinclair, spokesman for Yes to Fairer Votes, said: "These figures are very encouraging. We will continue to work hard on the ground to persuade people of our arguments." A senior Lib Dem source added: "Some people were very quick to write their AV obituaries. But as more people engage with the subject, especially through the work of the grassroots yes campaign, they are supporting the idea that we need to change our outdated electoral system."

In order for the referendum – a deal-clincher in the coalition negotiations – to happen on 5 May, the Parliamentary Voting System and Constituencies Bill needs to pass into law by 24 February. But with the House of Lords due to begin its spring recess on Wednesday, time is of the essence, and peers have been told by whips to prepare to delay their holiday if the Bill is not passed. Coalition nerves about winning key votes to overturn Lords amendments forced the cancellation of a planned trip by Nick Clegg and other ministers to Mexico next week.

The Prime Minister has faced accusations that the Tory leadership would be content to see AV adopted if it helped their junior coalition partner. But last week he urged Tory MPs to help him "to get the turnout up, particularly for the no vote".

This week, the No to AV campaign will unveil high-profile supporters, to counter the accusation that it is relying on members of the political establishment such as the former Labour cabinet ministers Lord Prescott and Margaret Beckett.