Election 2015: Mapping constituency opinion polls

Close constituency battles are being fought with less than a week to go before the general election, the latest opinion polls reveal.

Like all polls, these are snapshots, rather than a prediction of what will happen on 7 May and are subject to a +/-3% margin of error which may tip the result in some cases.

The map, shows the result of three by-elections and 174 constituency polls carried out by former Conservative peer Lord Ashcroft, Survation, and ICM between 1 March 2014 and 3 May 2015.

More than half of the constituencies surveyed (96) are marginal seats so it is perhaps unsurprising to see many showing a different result in polling than at the last election.

How the 177 seats break down in polling compared with 2010

If the results of these polls and by-elections were replicated at the general election, 93 of these seats would change hands and a further three are too close to call.

The Conservatives would hold 44 of the seats and gain 12 from the Liberal Democrats, but lose 44 to Labour.

Labour have a net gain, coming first in 44 Tory and 9 Lib Dem seats. Some polls have put them ahead in Nick Clegg's Sheffield Hallam constituency but the most recent survey by ICM on 3 May has the Lib Dem leader keeping his seat.

Labour may lose the seat where Gordon Brown is standing down and Jim Murphy's Renfrewshire East seat. Former Lib Dem leader Charles Kennedy (R) could lose the seat he has held since 1983

However, Labour's gains are offset by a massive swing to the SNP in Scotland, where 18 of the 19 Labour seats surveyed look set to change hands.

Among them are the seats of Scottish Labour leader Jim Murphy and shadow foreign secretary Douglas Alexander.

The SNP also take six seats from the Liberal Democrats in the polling, including the Gordon seat where former SNP leader Alex Salmond has thrown his hat in the ring, and former Lib Dem leader Charles Kennedy's seat of Ross, Skye and Lochaber.

Meanwhile, the sole Conservative Scottish seat of Dumfriesshire, Clydesdale and Tweeddale has the SNP ahead by 11 percentage points.

South Thanet battle

Research released this week suggests a close race between the Conservatives and UKIP in some constituencies in the east of England.

In South Thanet, where UKIP leader Nigel Farage is standing, a survey on 28 April finds the Conservatives on 34%, ahead of UKIP on 32% and Labour trailing on 26%.

But a poll just a few days earlier by Survation found a clear lead for UKIP on 39%, ahead of the Tories on 30%.

And in March ComRes found the seat effectively too close to call, with only one point separating the two parties and Labour.

In Rochester and Strood, which turned to UKIP at a by-election last year, a recent Ashcroft poll suggests the Tories are now back in the lead on 36 points, ahead of UKIP's 33.

But the research also finds the Conservatives trailing third behind UKIP and Labour in the highly marginal Essex seat of Thurrock.

Repeating polls

The Liberal Democrats hold on to 20 of their 46 seats polled but lose 12 to the Conservatives, including Business Secretary Vince Cable's Twickenham constituency.

However, repeating a poll can yield a different result as opinions change over time and different respondents simply have different views.

For example, in Cambridge, a Lib Dem seat since 2005, an Ashcroft poll last November put Labour in the lead on 33% and the Lib Dems second on 32% (statistically too close to call).

But the latest survey, also by Lord Ashcroft, has Labour on 31% and the Lib Dems with a clear lead on 40%.

Whether this and the rest of the 177 polls and by-elections will be mirrored when voters cast their ballots in the general election will not be known until 8 May.

Design by Laura Cantadori and James Offer, development by Mark Gerrard

Methodology

This data is taken from all published polling data in individual constituencies since 1 March 2014. Where a constituency was surveyed more than once, the most recent poll is shown.

Most of the polling shown was commissioned from independent polling companies by former Conservative party deputy chairman and donor Lord Ashcroft. Seven were conducted by Survation on behalf of UKIP donor Alan Bown or trade union Unite. One was carried out by ICM for former Lib Dem peer Lord Oakeshot.

Ashcroft and Survation polls canvas 1,000 people by telephone and have a margin of error of +/-3% at 95% confidence level. The ICM poll sample size was 501 and margin of error is +/-4.5%.

The Ashcroft question used is the one which invites respondents to think about their constituency.