A review of Tuesday's incidents is taking place

The apology came after London Underground (LU) users faced one of the worst days for delays on the network.

LU's chief operating officer Mike Brown said he was "very sorry" for the problems "which affected many lines but were unrelated".

Signalling problems were blamed for the suspension of various lines throughout Tuesday.

At one point 1,000 passengers were stuck just 50 yards outside Warren Street station when a Victoria Line train stalled.

'Urgent review'

This caused the suspension of part of the busy line, which runs from north to south London, for 45 minutes during the evening rush-hour.

The line had already been suspended during the day due to a defective rail.

Other suspensions also caused problems for passengers on the Metropolitan, District, Hammersmith and City, Northern, Jubilee and Circle lines.

Mr Brown said he would be carrying out an urgent review of all the incidents with Tube maintenance firms Metronet and Tube Lines.