An ICM poll for the Guardian finds that Labour are still four points ahead of the Tories on general election voting intentions.

Despite its troubles over Iraq and immigration, the government fell only one point to 37 per cent in the past month.

The Tories remain stuck on 33 per cent and the Liberal Democrats also fell one point to 21 per cent.

But all three major parties suffer from the extra coverage given to minor groups in the European election campaign.

One in four voters may switch parties next month while "others" have risen two points in the past two months in general election intentions.

The poll also shows there would be four per cent greater support for Labour under Gordon Brown as leader than there is for Tony Blair, at the expense of the Lib Dems and others.