David Cameron faced a furious rightwing backlash on Friday, as the Conservatives reeled from a double by-election defeat, handing Gordon Brown a strong end to the political season.

A senior Tory MP told the Financial Times the Cameron project risked “imploding”, as some activists questioned whether the opposition party should consider electing its sixth leader in a decade. While there is as yet no suggestion that the disillusion spreads across the party, a former frontbench Conservative MP warned Mr Cameron faced a “difficult” autumn party conference if he failed to reverse Labour’s opinion poll bounce.