The crash has cost LU �40m

The London Underground (LU) report was also critical of safety procedures both before the Central Line accident and on 25 January when 32 passengers were injured in the crash.

But the inquiry panel, which was independently-chaired, said it was still not possible to give the root cause of the accident in which a traction motor attached to the underside of the train came loose and fell on to the track, derailing carriages.

Following the derailment the line was suspended, but after weeks of disruption it is expected to be fully reopened on Saturday.

'Management weakness'

The panel also spoke about unqualified staff and a lack of leadership on safety matters and said employees had spoken about "long-term management weakness" which had led to problems on the line.

LU managing director Paul Godier said: "This report doesn't pull any punches. It identifies a range of deficiencies that need to be put right."

Bob Crow, general secretary of the Rail Maritime and Transport union, said: "The communications breakdown that allowed Chancery Lane to happen despite a catalogue of earlier incidents is now hampering the very inquiry into its causes."

The report found that the gearbox, which was attached to the traction motor, had not been overhauled for about 10 years and its manufacturers had recommended it be serviced after 4.5 years.

It also said couplings involved in the Chancery Lane accident were significantly damaged which had been observed after two earlier Chancery Lane-type incidents.

The Central Line disruption has cost LU �40m, while the cost to the London economy is thought to be about �275m.