Offshore giant Shell has been accused of breaking safety rules at its site at the huge St Fergus gas terminal.

The Health and Safety Executive (HSE) has issued an improvement notice for the second time in just over a year after it emerged not enough was being done to prevent “major accidents” at the complex north of Peterhead.

The HSE accused Shell of failing to take “all measures necessary” to identify tasks which had the potential to cause a “critical” situation.

It told the company: “You have failed to adequately identify the safety critical tasks which have potential to initiate, escalate, recover from, or mitigate the consequences of, a major accident at the St Fergus gas plant.”

It is the second time Shell has been criticised by safety chiefs for failings at its St Fergus operation.

At the end of 2013, the HSE acted over the methods used to lift material in areas near equipment filled with gas.

Inspectors feared a major accident could happen, and that not enough was being done to protect staff and the environment.

By the time the breaches were made public, Shell said it had already acted on the warning and the safety of its staff was a top priority.

Last night, a spokeswoman for the company said: “Shell can confirm that it was issued with an improvement notice in relation to the management of safety critical tasks at our gas plant at St Fergus near Peterhead.

“Action is being taken to address the issues raised. The safety of our people and surrounding community remains our primary concern.”

The terminal has created tens of thousands of jobs in Buchan since it opened three decades ago.

The first gas was received at St Fergus in 1977 from the Frigg field in the Norwegian sector of the North Sea.

The Queen inaugurated the terminal in May 1978.

St Fergus receives gas from more than 20 fields in the North Sea and, on an average day, processes about 20% of the UK’s gas requirements.

Total and ExxonMobil are the other two main operators at the terminal.