Seven people were taken to hospital after the Camden crash

The Health and Safety Executive (HSE) report exposes thousands of examples of "substantial non-compliance" - most concerning the condition of the track.

It also highlights the varying quality of track inspections.

Following derailments at Hammersmith and Camden Town earlier this month, LU said inspection procedures were adequate.

But in its response to the HSE report - issued in May - it admitted there were problems.

The HSE internal report was seen by BBC television's Kenyon Confronts programme.

Manual track assessment is not being done at the required frequency due to lack of competent staff LU spokesman Jarvis investigated again

During the run-up to the Underground's part-privatisation in February and March, the HSE had conducted a far-reaching inspection.

It blamed the variable quality of track inspections across the network on staff shortages and pressure on resources.

In its response, LU said: "Manual track assessment is not being done at the required frequency due to lack of competent staff."

Tube chiefs are now considering the frequency of testing in the wake of the derailment at Camden Town station.

On 19 October seven people were injured at the north London station, when the rear carriage of a Northern Line train came off the track and hit a wall.

Camden Town station will remain shut until further notice

Investigations are still continuing about the cause of the incident.

The accident came 48 hours after a Piccadilly Line train derailed at Hammersmith, which was believed to be caused by a cracked rail.

Ballot papers are due to go out next week to members of the Rail Maritime and Transport union over possible strikes and "go slows" following the derailments.

RMT general secretary Bob Crow said drivers would be asked to reduce speeds as part of a campaign of industrial action that would cause "complete chaos" to Tube services in the run up to Christmas.

'End the madness'

Drivers could be told to slow down to just 20mph (32.2 km/h).

The union has been called to a safety summit with LU on Tuesday.

But Mr Crow said he would not tolerate any compromise on safety.

On Monday the RMT stepped up calls for maintenance of LU to be taken away from private firms

A union spokesman said the "madness" had been ended on railways following the decision by Network Rail to take maintenance contracts from private companies and it was time to end the "madness" on LU.

• Kenyon Confronts is on BBC 1 at 1930 GMT on Wednesday.