Latest opinion poll, carried out three weeks before AV referendum, suggests opinion against alternative vote system is hardening

This article is more than 9 years old

This article is more than 9 years old

Support for a change to the way in which MPs are elected is collapsing, according to a new Guardian/ICM poll.

The figures give the No campaign a 16-point lead, compared with a two-point lead for the Yes campaign in the equivalent Guardian/ICM poll, carried out in February.

Conducted less than three weeks before the UK votes, the poll suggests opinion against the alternative vote is hardening as both sides squabble over the implications of change.

The poll is the first for two months to be carried out by telephone using a random sample rather than an online panel, and the results have been adjusted to take account of turnout.

Uniquely for the Guardian, the poll also includes a sample of voters from Northern Ireland, which is included in the UK-wide referendum.

ICM posed the same question that will be asked in the referendum: "At present, the UK uses the first past the post system to elect MPs to the House of Commons. Should the alternative vote system be used instead?"

The results will make depressing reading for Yes campaigners, who began the year with high hopes. A December Guardian/ICM poll last year put the Yes vote six points ahead before adjusting for likely turnout.

In February, the two camps were neck and neck on the same measure, and now – again before turnout is taken into account – the No vote is 11 points ahead.

Pro-AV campaigners had hoped people who wanted change would be more likely to turn out on polling day. Instead, once people are asked how likely they are to vote, the lead for the Nos increases.

Among people who say they are likely to vote and have made up their minds, the No lead is now 16 points, with 42% saying yes and 58% no.

Three-quarters of Conservatives are planning to vote will vote against, as will a small majority of Labour supporters. Only Lib Dem voters are firmly in favour, with more than two-thirds saying they will vote for the change.

The Yes camp could still turn things around by winning over the 23% who say they do not know how they will vote, but this includes many people who say they may not turn out at all.

Young people are more than twice as likely to favour AV as pensioners, but pensioners are more than twice as likely to vote as the young. Increasing youth turnout could determine the outcome.

Ahead of the elections, which will take place in Scotland and Wales for devolved administrations and in England for many local councils, Labour has also regained a narrow lead over the Conservatives.

The estimated national voting intentions put Labour on 37%, up one. The Conservatives are on 35%, down two, and the Lib Dems on 15%, down one but still higher than in most online polls.

Support for other parties stands at a combined 13%, a recent high in ICM surveys. That includes 3% each for the Greens and Ukip and a combined 5% for the Welsh and Scottish nationalists.

• ICM Research interviewed a random sample of 1,033 adults across the United Kingdom aged 18+ by telephone on 15-17 April 2011.

Interviews were conducted across the country and the results have been weighted to the profile of all adults. Voting intention based on British sample of 1,003 people.