'David Davis effect' cuts into Tories' poll lead

David Davis's sudden resignation triggered a seven-point collapse in Conservative support, a new poll indicates today.

The results, which will cause alarm among David Cameron's inner circle, show a clear "David Davis effect" in the aftermath of his surprise by-election gamble.

The ComRes poll for The Independent on Sunday reveals that before 1pm on Thursday – the time of his resignation announcement on live TV – the Tories were on 48 per cent, 22 points clear of Labour on 26 per cent.

But after the announcement, which took Westminster by surprise, Tory support dropped to 41 per cent, 15 points ahead of Labour. The two-day survey puts the Tories on 44 per cent overall, up one point on last month. Labour was unchanged at 26 per cent, while the Liberal Democrats have fallen two points to 17 per cent.

But a separate poll for The Mail on Sunday showed significant support for Mr Davis in his constituency. In the ICM survey, some 59 per cent of those polled in Haltemprice and Howden said that they would vote Tory against 26 per cent for the Lib Dems and 12 per cent for Labour.

The Tories' 18-point overall lead in the IoS poll will not be cause for celebration in Downing Street. However, voters believe that Gordon Brown is still a better Prime Minister than the two strongest Labour contenders for his job. Some 45 per cent disagreed that Alan Johnson would be better in No 10, against 40 per cent who agreed, while 46 per cent disagreed David Miliband would make the better candidate, against 41 per cent.

ComRes telephoned 1,012 adults for The IoS. The full tables are at comres.co.uk