Labour soar past Tories to take seven-point lead in latest ICM poll

Poll comes after resignation of Sayeeda Warsi over Gaza and Boris Johnson's return-to-parliament pledge

Ed Miliband has taken advantage of a bruising week for David Cameron to take a seven-point lead in the latest Guardian / ICM poll. Photograph: Rex

Ed Miliband has overturned a narrow Tory advantage to take a commanding seven point lead after a bruising week for David Cameronin the wake of the resignation of Baroness Warsi over the Gaza crisis, according to a new Guardian / ICM poll.

In a boost for Labour, which is embarking on a pre-election summer campaign called The Choice, the party has seen its support increase by five points over the last month to 38%, a share it last recorded in March. The Tories see their support fall by three points to 31% – last recorded in June – giving Labour a seven-point lead. In last month's Guardian / ICM poll the Tories had a one-point lead over Labour – 34% to 33%.

The Liberal Democrats are unchanged on 12%, while Ukip sees a one-point increase in its support to 10%.

The poll, carried out between Friday and Sunday, followed a difficult week for the prime minister after Warsi resigned from the government after criticising the prime minister for his "morally indefensible" decision not to criticise Israel for disproportionate action in Gaza. On WednesdayBoris Johnson signalled his intention to return to parliament at next year's general election, placing him in a strong position to replace the prime minister.

The London mayor is the dominant figure in the race to succeed Cameron, according to the poll which shows nearly a third of voters (29%) believe he should be the next Tory leader. Theresa May, the home secretary who is seen as the current frontrunner, has the support of just 14% of voters. George Osborne, the prime minister's preferred candidate, is in third place on 6%. Jeremy Hunt, the health secretary who is seen as a leadership contender, is on 2% – the same level as the chief whip Michael Gove who is one of the chancellor's strongest supporters.