A second train was derailed last night - just as rail chiefs were disclosing the locations of known danger spots on Britain's railways.

Railtrack revealed 81 locations on railways where the track featured "similar characteristics" to the one suspected of causing the Hatfield rail disaster, which claimed four lives.

And senior union leader Bob Crow of the Rail, Maritime and Transport union, said Railtrack had warned its maintenance company, Balfour Beatty, that there was a major derailment risk in the Hatfield area seven months ago.

No one was injured in last night's derailment, which happened at 17.43pm, just south of Stafford station, when the locomotive and front two carriages of the 16.47pm Virgin Cross Country train from Birmingham New Street to Manchester Piccadilly went off the rails.

It came as Railtrack executives met all the train operating companies and contractors to review initial findings of the causes of the disaster at Hatfield, Herts which claimed four lives.

The company's chief executive, Gerald Corbett, returned to his desk after his offer to resign was rejected, but faced mounting criticism of his company's stewardship of the railways.

Before going into the meeting, he declared: "No broken rail is acceptable", but said the industry had not received adequate investment for years and urged critics to be "realistic".

The company earlier alarmed critics by confirming it had identified the 81 track locations similar to track at Hatfield and listed the spots, with the ''precautionary'' speed restrictions now in place on them - as low as 20mph in places.

Delays of varying lengths were expected to hit passengers travelling on those sections of line.

As rail chiefs tried to find answers to the Hatfield incident, Mr Crow claimed he saw a letter from Railtrack to sub-contractor Balfour Beatty warning there could be a derailment because of a repairs backlog.

The letter suggested 82 per cent of track defects in the Stevenage area and 33 per cent of defects in the Doncaster area had never been rectified and all of the faults listed could lead to a derailment, he said.

Balfour Beatty said the fault list was compiled without latest records of what had been completed, and little of outstanding work needed to be done by the time the company received it.

Railtrack's preliminary view is that a broken rail caused the crash on Tuesday, in which four people died and 35 were injured when a GNER express came off the rails at Hatfield.

Today, the Health and Safety Executive will issue a preliminary report on the Hatfield rail crash, Transport Minister Lord Macdonald told the House of Lords. He said the Government would redouble efforts to make railway safety a top priority.

Visit the Railtrack website for further information.