The train and tunnel wall were badly damaged at Camden Town

Tim O'Toole told an emergency session of the London Assembly's transport committee that more needed to be done to restore public confidence following two derailments at the weekend and the shutdown of the Victoria Line in the rush hour on Wednesday.

The assembly's transport committee held a special meeting on Thursday with LU, the heads of the two private consortiums in charge of track maintenance and unions.

A Tube safety summit called by London mayor Ken Livingstone will take place next Tuesday.

But Mr O'Toole admitted to the committee that safety procedures would have to be changed.

Train evacuated

The unions accused Tube managers of reducing safety checks, saying that on one section of the Central Line six people were doing the job that used to be done by 26.

The Rail Maritime and Transport (RMT) union also claimed a "potentially serious" incident was averted on 11 October when a driver decided to evacuate a train and take it out of service because of a defect.

It said the train had a seized axle which could have resulted in a derailment if it had continued, but LU accused the RMT of exaggerating the incident.

Seven people were injured on Sunday morning when the rear carriage of a Northern Line train came off the track and slammed into a wall at Camden Town.

No-one was hurt in a derailment at Hammersmith on Friday evening which has been blamed on a broken rail.

Safety concerns

The RMT has given Tube bosses until noon (1200 BST) on Friday to answer its safety concerns or face a strike ballot.

Parts of the Northern Line will remain shut until at least next week while engineers work to repair damage caused when the Tube train derailed.

There are no Northern Line trains running from East Finchley to Euston and between Golders Green and Charing Cross - rail replacement buses are ferrying thousands of passengers to affected stations.

A report into the Camden derailment is expected by the end of November and another into the Hammersmith incident within three weeks.