Denis Tunnicliffe, London Transport's chief executive, was criticised by a Commons Select Committee for not having contingency plans in the event of the extended underground line not opening in time.

Mr Tunnicliffe admitted the effect of the Millennium Dome celebrations, set to attract 70,000 visitors a day, would be "dire" if the extension was not completed.

He said: "We will take steps to make a contingency plan at an appropriate time if we are unable to adhere to the promised objective."

In a two-hour session with the Culture, Media and Sport Committee he was told the panel of MPs had "lost faith" in his latest completion forecast.

A year ago MPs were told the connection might be completed by September 1998

Gerald Kaufman MP read minutes from the committee inquiry with London Transport exactly a year ago in which Mr Tunnicliffe promised the line would be completed by September 1998.

Mr Kaufman said: "You told us there was definitely a 'better than even' chance of the line opening by the end of September 1998.

"We are now a year on from that. You are now asking us to have faith. Why should we have any greater confidence?

"My faith is rapidly diminishing."

Mr Tunnicliffe, who rejected a call from Christopher Fraser MP to resign for his handling of the project, blamed current industrial action by electricians and complex work on the project for the further delays.

The strategy for opening the Jubilee extension has been dogged by delays.

London Transport changed from opening the extension as a whole in September 1998 to Spring 1999, and now to one of opening in three phases during the period of Spring to Autumn 1999.

The date of completion of the three phases set by London Transport are: