Labour’s uneasy summer truce ended on Wednesday when Charles Clarke, the former home secretary and staunch critic of Gordon Brown, warned that the party was heading for “utter destruction” at the next general election unless it changed.

Mr Clarke insisted there was no “Blairite plot” to oust the prime minister, but said there was a “deep and widely shared concern” among many Labour MPs about the direction the party was taking. His comments in the New Statesman magazine will add to tensions in the party at a time when Mr Brown is struggling to reassert his authority at the start of the new political season.