Liberal Democrats have called on the mayor to do more to catch fare dodgers in London.

The move came as figures revealed that bus ticket inspectors have on average caught just one offender each for every day Ken Livingstone has been in City Hall.

In over four years in office the mayor has overseen only 246,000 fines being handed out by between 135 and 200 officials.

Lib Dem London assembly members are calling for the penalties to be increased as a deterrent and to stop fare-paying passengers picking up the bill.

"It is vital that the mayor and Transport for London urgently target and catch persistent fare dodgers so that the message gets hammered home that this is a criminal offence," said transport spokesman Lynne Featherstone.

Meanwhile, Livingstone has confirmed that he will increase the congestion charge for cars to "at least £6".

He told the BBC this week that the central London road toll will be raised by a minimum of £1 per day.

"I don't like putting up taxes and fares... you put it up the minimum you need to, to do what you have got to do. It won't be less than a pound," he said.