It has been difficult to establish blame in the crash

Train drivers' union Aslef has demanded to know why it was taking so long to get to get to the root cause of the Potters Bar crash which happened a year ago on Saturday.

It also called for a law to punish corporations who put workers or members of the public at risk.

Aslef general secretary Mick Rix said: "My concern is that safety is being swept under the carpet.

"Is it politics or bureaucracy that is causing the delay?"

Mr Rix said the victims of the Potters Bar crash, as well as their families, railway workers and the travelling public should be given answers so that a similar tragedy could be prevented.

He said: "Potters Bar is not the only case for concern.

"We were refused an independent inquiry into the (January 2003) Chancery Lane accident on the London Underground, and we are still waiting for the full report into the Hatfield disaster.

Mr Rix added: "It is also time for the Government to introduce a new law against corporate killing, as promised by Labour in its 2001 election manifesto."