Deputy Prime Minister John Prescott announced the move following a report from the Health and Safety Commission.

The report, commissioned by Mr Prescott last year, raised a number of concerns about the way in which Railtrack - which is responsible for the rail network - regulates safety.

And Mr Prescott said he was "extremely concerned" about some of the findings.

The investigation will be carried out by independent experts appointed by the Health and Safety Commission.

Key areas for concern

Mr Prescott made the announcement following a two-hour meeting at 10 Downing Street with Prime Minister Tony Blair, Transport Minister Lord Macdonald and senior figures from the rail industry to discuss Tuesday's Paddington train disaster.

He said the meeting had covered safety measures on the network, the inquiry which has been set up under Lord Cullen into the disaster and a separate investigation into the Automatic Train Protection (ATP) safety system.

The Downing Street meeting discussed rail safety for two hours

Lord Macdonald is to make a further statement to the House of Lords on Monday.

The Health and Safety Commission report, which was ordered after the Commons' Environment and Transport Select Committee voiced its fears to Mr Prescott's department last year, is reported to have identified five key areas for concern.

It questions whether Railtrack should remain responsible for approving safety rules and procedures, for railway standards development, for safety auditing and for strategic research.

Action on signals promised

It suggests other bodies could take over responsibility for these areas.

The report is also reported to question whether the investigation of accidents should be further separated from Railtrack's area of responsibility.

The Downing Street meeting was attended by rail regulator Tom Windsor, Health and Safety Commission chairman Bill Callaghan, chief railway inspector Vic Coleman and head of the Strategic Rail Authority Alastair Morton.

Earlier, Railtrack said it was working to reduce the number of trains passing signals at danger, which it said had happened 643 times last year, a figure it described as "wholly unacceptable".

However, it added that in about 80% of the incidents the train over-ran the signal by less than 100 yards.

"Whenever a signal is passed at red there is a management investigation," Railtrack chief executive Gerald Corbett told Radio 4's Today programme. "The reasons for passing at red are complex."

He said that Railtrack was looking at installing the Train Protection Warning System - which would automatically stop trains from going past red signals - earlier than the scheduled date of 2003.

Railtrack also defended itself against media accusations that it had ignored driver complaints that signal 109, which the Thames train passed and which the Health and Safety Executive has banned from use, was hard to see.