AN OPINION POLL has shown that public support for scrapping the first-past-the-post (FPTP) system used for Westminster elections has fallen, less than three weeks before the matter is put to a public vote.

Ahead of the referendum on May 5, a poll carried out by ICM and commissioned by the Guardian has shown that support for replacing the FPTP system with a modified version of proportional representation – the Alternative Vote (AV) – has fallen massively since the last similar poll in February.

The anti-AV camp now commands a lead of 16 percentage points, 58-42, compared to the last such poll which had both sides virtually neck-and-neck and with the Yes camp claiming the lead before Christmas.

When likely turnout is taken into account, the lead is adjusted to 11 points – which is also the margin of the lead when ‘don’t know’ votes are included, with 44 per cent of respondents committing to voting No and 33 per cent supporting Yes.

While 23 per cent of voters remain undecided, the overall trend in polls being carried out by other newspapers is certainly towards the anti-AV side.

Hours before the poll results were released, prime minister David Cameron reiterated his opposition to the move, saying AV would “take away” some of the power of an individual vote.

The Alternative Vote, Cameron added, would result in coalition governments becoming a more common reality – which then would make politics “less accountable”.

Cameron was joined by former Labour minister John Reid – while current Labour leader Ed Miliband was simultaneously attending a  pro-AV rally with the Liberal Democrats’ Vince Cable.

The referendum – which will be only the second referendum to take place across all of the United Kingdom – will take place alongside elections to regional assemblies in Scotland, Wales and England, and a number of council elections in England.

Voters in Scotland, Wales and Northern Ireland are considered more likely to support the referendum, given that their local assemblies and governments are elected through systems that are slightly more complex than the FPTP method, which awards victory simply to the candidate with the highest number of votes.

Provision for the referendum was one of the Liberal Democrats’ key demands when entering coalition with Cameron’s Conservatives last year.