MPs to push through 5 May referendum on voting system change

MPs are expected to push through a bill this week to hold the vote in just over two months' time, on the same day as the Holyrood election.

Their decision is expected as new figures by polling company ICM, commissioned by the pro-reform lobby, show that a change from first-past-the-post to the alternative vote (AV) is supported 62 per cent to 38 per cent in Scotland - the highest level of support in the country.

The Yes campaign claims that the figures are due to the fact that support is higher in parts of the country - such as Scotland - where different electoral systems are already in place.

Under AV, voters would rank candidates in order of preference, rather than simply backing one or the other.

Candidates have to gain 50 per cent of the support of constituents before getting elected.

However, David Cameron, the Prime Minister, is expected to make a speech this week setting out why he believes the country should stick by first-past-the-post.

The move means he will be going head-to-head against the Deputy Prime Minister, Nick Clegg, who insisted the referendum be held as part of the coalition pact between the Tories and the Liberal Democrats.

Mr Cameron's early intervention in the No campaign this week is being seen as a way of heading off any internal party criticism that he will "soft-pedal" in the election in order to allow Mr Clegg a crucial victory.

Coalition insiders fear that a loss for Mr Clegg will pile further pressure on him this summer to pull out of the pact.

A spokesman for the Yes campaign last night said they believed the public mood was growing for change. He said: "We are pushing ahead in places like Scotland where we have had a different electoral system already. After the expenses affair, people now want some form of change.The key message for us is that this is a system which will make MPs work harder, by making them reach out to more of the community"

However, the No campaign warns that the new system would be complex and expensive, and would lead to more hung parliaments with the Lib Dems as permanent kingmakers.The No campaign is expected to be led by leading figures in the Conservative and Labour camps, including the Foreign Secretary, William Hague, and the former home secretary, David Blunkett.

The decision to press ahead with the referendum on 5 May will be controversial in Scotland, as it will mean voters having to decide on both it and the Holyrood election.

Both Labour and the SNP have insisted the decision is wrong, and have called on the UK Government to shift the date.

Earlier this month, Scotland's returning officers said that many councils would delay counting the Holyrood vote until the day after polling partly as a result of the extra workload.

However, UK ministers insist the decision to have one election day will save millions of pounds.