A government inquiry into a new system for elections to the House of Commons will not now take place after a revolt by senior Cabinet ministers.

John Prescott and John Reid blocked the move, which was to be announced this week to fulfil a commitment from the Labour election manifesto in 2001.

Both ministers said it would be unacceptable to go ahead. Jack Straw and David Blunkett also opposed the plan.

Lord Falconer had drawn up plans for the inquiry.