He said plans for motorists to pay a �5 daily fee to travel into central London might not happen until after the 2004 mayoral elections.

The congestion is so bad you should do something about it

Mayor Ken Livingstone

Speaking on BBC One's Breakfast With Frost, he said: "It could come in about a year or I could put it off until after the election," he said.

But he indicated that he would still prefer to go ahead with the measure before Londoners voted in the elections.

He accepted that the plan, which is expected to raise up to �150m in revenue, was unpopular.

Weekday charge

"It does seem to me, if you can do it, the congestion is so bad you should do something about it, not try to con people," he said.

Ken Livingstone hopes to cut traffic by 15%

"People should have the right to see if it works before they decide whether or not to vote for me again."

The fee aims to help money to improve public transport by charging motorists for driving into central London between 7am and 7pm on weekdays or face a �100 fine.

The congestion charge is part Mr Livingstone's plan to cut traffic by 15%.

It has yet to gain government backing, with a final decision expected in March.

Critics of the scheme say it will unfairly penalise commercial vehicles which need to move in and out of the charge zone several times a day.