New Labour was reconstructing the British system of government, Mr Benn said. "The Prime Minister has assumed the power of a president, using the royal prerogatives that have survived since the middle ages, his huge parliamentary majority and his tight control of the Labour Party machine to be sure that he always gets his way."
The attack was the latest evidence of continuing unease between Old and New Labour and came amid reports that grassroots members were planning a revolt at the party's annual conference.
Writing in Tribune, the Labour weekly, Mr Benn, 74, accused the Prime Minister of destroying traditional activism and trying to convert Britain into a one-party state. "The Labour Party conference has been converted into a rally to provide a platform for the leadership and the National Policy Forum has become a device to prevent real issues from coming to conference."
Mr Benn, MP for Chesterfield, said Mr Blair could demand all future Labour MPs pledge support for issues such as the euro and proportional representation or risk expulsion. "The process of winding up the Labour Party would then be virtually complete and the electors would have no real choice on polling day.
"If this is the plan Britain would have been converted into a one-party state with serious consequences for us all."