Labour increased its opinion poll lead over the Conservatives by three points last month, according to an ICM poll for the Guardian.

The survey, which took place after the Budget, gives Labour a 40 per cent share of the vote, eight points ahead of the Tories and enjoying its biggest lead since December.

The Tories are two points down on last month to 32 per cent, with the Liberal Democrats on 20 points.

The poll also found that 30 per cent of the high-turnout "grey voters" - those over 65 -are more likely to vote Labour.

The poll also suggests that Labour is leading the Conservatives on seven out of the eight key issues that voters say are most important to them.

The only area on which the Tories are  enjoying a lead is asylum and immigration.

The Budget was a net vote-winner, with 20 per cent of all voters saying they were more likely to vote Labour as against 14 per cent who said it has put them off.

But 44 per cent of pensioners will vote Tory, according to an ICM poll for Saga magazine.

The Lib Dems, meanwhile, today begin a £100,000 pre-election PR blitz.