Lieutenant Commander Len Louw is under investigation at Faslane naval base on the Gareloch amid reports he had been drinking.

Colleagues raised concerns when the weapons engineering officer arrived for work on HMS Vigilant last month.

The Scottish Sun has reported claims the submariner was “staggering drunk” when he came on board the £3 billion vessel.

HMS Vigilant – one of Britain’s four Vanguard-class submarines which carry up to eight Trident missiles armed with nuclear warheads – was docked at a US naval base at the time.

The BBC is reporting they understand the officer had been drinking the night before and was carrying a bag of leftover chicken from a barbecue for his lunch.

HMS Vigilant is normally based at Her Majesty’s Naval Base Clyde at Faslane in Argyll and Bute, but at the time of the incident in September, it was undergoing maintenance at the Kings Bay facility in Camden County, Georgia.

The weapons engineering officer is responsible for all weapons and sensors on board.

It is not yet clear if drink was the reason why Lt Cdr Louw was judged unfit to carry out his duties, but due to the responsibilities of his job, he was sent back to the UK pending an investigation.

A Royal Navy spokesman said: “An investigation is under way therefore it would be inappropriate to comment further.

“However, where an individual’s conduct falls short of the high standards we expect, we won’t hesitate to take the appropriate action.

“While we don’t comment on the detail, there are numerous safety checks and processes to protect the safety and use of weapons aboard all submarines.”

It is not the first time HMS Vigilant’s crew has made the headlines.

In October 2017, a captain was relieved of his command after an alleged “inappropriate relationship” with a female member of his crew.