Figures show the commissioner's salary in 2002 was �316,000

The London Assembly's Liberal Democrats claim Bob Kiley stands to be paid up to �365,000 on top of his �312,000 salary.

A Lib Dems spokeswoman said questions must be asked whether the targets are what Londoners expect to be delivered.

Transport for London (TfL) defended the bonuses saying said they had delivered some "real achievement".

Investment programme

Statistics gained by the Lib Dems showed the commissioner's salary for 2002 was �312,000, and his total payout, including salary and all bonuses and benefits, was �700,925.

The Lib Dems' transport spokesperson Lynne Featherstone said: "Bonus payments are meant to be for achieving more than what is expected, yet the extra cash given to Mr Kiley appears to have been paid for simply doing his job."

Defending TfL's record, a spokesman said bus use had risen by a third since 2000.

He added: "Efficiencies and financial management will save more than �1bn by the end of the decade and TfL has just embarked on a �10bn, five-year investment programme."

TfL's remuneration committee will set the size of the bonus in May.