The Labour government on Wednesday lifted the top rate of income tax to 50 per cent, ripping up a central promise of its 2005 election manifesto and drawing a clear ideological dividing line with the opposition Conservative party.

In a highly political Budget, Alistair Darling, the chancellor, cited “fairness” as his motivation for raising income tax from next April for people earning more than £150,000 a year, cheering many Labour MPs.