The poll of 301 GPs found that 48 per cent planned to vote for the Conservative party at the next election, up from 35 per cent in 2005. Many said they were unhappy with the government over health issues.

It is dissatisfaction with Labour policy and the unpopularity of the Liberal Democrats rather than any particular policy that is driving Conservative party popularity.

Labour backing dropped from 31 to 23 per cent over the same two-year period, with GPs blaming the pay freeze, 'GP bashing' and a failure to deliver an improved NHS.

While a mid-term fall in government support and rising enthusiasm for an opposition party is far from unprecedented, the poor showing of the Liberal Democrats is noteworthy.

Like Labour, the Liberal Democrats have haemorrhaged support since 2005, with their popularity falling from 19 to 13 per cent. The main reasons given were the unpopularity of party leader Sir Menzies Campbell and a lack of belief in the party's ability to win an election.

Surveys were completed between 11 July and 21 August.

The results contrast with national polls suggesting that new Labour leader Gordon Brown is enjoying a bounce in support and faith in Conservative leader David Cameron is dwindling.

The national polls have fuelled speculation at Whitehall that Mr Brown could call a election as early as autumn or spring 2008.

However, an ICM poll in Monday's Guardian is more in keeping with the GP survey's findings. It puts Labour support up by 1 percentage point on July to 39 per cent, Conservative backing up 2 to 34 per cent and the Liberal Democrats down 2 to 18 per cent.

Participants in the GP survey were asked which policy change they would most like to see the government make. The most popular answer was an independent NHS without politicians, at 15 per cent. Ten per cent wanted no or less change, 7 per cent backed greater GP autonomy and 4 per cent wanted either troops out of, or an apology about, the Iraq war.

The devolved governments in Scotland, Wales and Northern Ireland fared better than the national UK government.

Of the 48 GPs polled in these three countries, 31 per cent described devolved government performance as good or very good compared with 17 per cent for the UK government and 35 per cent as poor or very poor, against 47 per cent for the Westminster team.

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