Whitehall 'Sir Humphreys' will ambush the Bill to set up the North-East elected assembly in a bid to weaken its powers, MPs were warned today.

Tony Travers, a leading local government academic, told a Commons committee that Government departments would launch a last-gasp fight to retain control.

A fierce behind-the-scenes battle had taken place during passage of the legislation to create the Greater London Assembly - the last significant act of devolution.

Mr Travers said: "The more that power is transferred downwards from the centre, the greater the threat to the baronies of Whitehall.

"It is almost certain that the passage of legislation to create regional government in England would face similar obstacles."

Professor Travers, of the London School of Economics, was giving evidence to the office of the deputy prime minister select committee inquiry into the draft regional assemblies Bill.

He told the MPs there was a real concern that the regional assembly's powers - rather then being devolved down from Whitehall - would be transferred up from local authorities.

Mr Travers said: "County planning, fire and emergency services, the police and even transport could, according to some proposals, be transferred from local to regional government.

Furthermore, the assembly would be weakened by its ability to raise "only a modest council tax precept, to cover administrative costs". It would not be "autonomous and confident" unless it was able to raise income equivalent to 50% of its budget, Mr Travers said.

The academic also urged to government to consider a directly-elected "governor" of the assembly government to give its leader more "visibility".

Bernard Jenkin, Tory devolved government spokesman, said: "The government wants to create an expensive assembly with no real powers, controlled by Whitehall but paid for by taxpayers in the North East."