Investigators will look at how crashes are caused and work to improve safety and reduce the number of accidents.

The body has been set up following an inquiry into the cause of the Ladbroke Grove crash which killed 31 people in October 1999.

All systems

It will investigate accidents on mainline, metro, light rail, heritage and some cable rail systems.

Alistair Darling, Secretary of State for Transport, said: "The launch of RAIB puts the investigation of rail accidents on a new footing.

"The RAIB has the important responsibility of ensuring the causes of accidents are identified as quickly as possible, shared publicly and effective recommendations are made to prevent similar occurrences."

Any investigations will be independent and will be carried out alongside those conducted by industry regulators, the police and the Health and Safety Executive.

The RAIB will report its findings directly to the Secretary of State for Transport.