Tony Blair could face a substantial backbench revolt over his decision to replace the Trident nuclear weapons system, it has emerged, with moderate Labour MPs joining forces with leftwingers to try to delay approving up to £20bn of government spending on the project.

In an interview with the Financial Times, Jon Cruddas, the Labour MP for Dagenham and one of several contenders in the race to replace John Prescott as the party's deputy leader, said a rebel amendment calling for a longer debate was likely to be tabled ahead of a crunch Commons vote ex-pected on March 14.