Rail accident investigators raised the alarm yesterday over potentially disastrous safety problems still not addressed by the industry years after being discovered.

Their annual report details a raft of findings after probes into incidents including derailments and collisions on the network.

But Rail Accident Investigation Board (RAIB) chief inspector Carolyn Griffiths warned that dozens of recommendations had gone unheeded - with 25 still not addressed after three years.

The 2008 derailment of two massive diesel locomotives at a Somerset junction was among the cases where action had yet to be taken.

Investigators found staff fatigue had played a part in the incident, but six years later Network Rail still allows working weeks of up to 72 hours.

In another case the RAIB advised action following a repeat of a fatal incident near Hereford to ensure that a level crossing is not raised in error as a train approaches.

Yet four years on from the 2010 accident Network Rail has yet to identify the crossings at risk.

Ms Griffiths said there were "a number of recommendations where we have particular concerns over the adequacy of the actions taken by the industry, and consequently the risks we noted during our investigations may still not be adequately addressed."

Rail union RMT said the delays were "wholly unacceptable."

Its general secretary Mick Cash said: "We have repeatedly warned that budget constraints, fragmentation and casualisation remain the major threats to rail safety and that those risks will be heightened as the network struggles to cope with surging demand.

"There must be no further slippage on the implementation of key safety recommendations."