The move marks another sea-change away from ancient tales of sailors enjoying a drink, fuelled in part by the traditional daily ration, or "tot" of rum.

This would be handed out to Royal Navy personnel for about three centuries until the practice was ended in July 1970.

Under new rules unveiled this week, Royal Navy personnel should consume no more than three units of alcohol per day or 14 units of alcohol per week regardless of rank when at sea, a defence source told AFP, asking not to be named.

Each vessel will be required to go teetotal at least two days per week and zero and low-alcohol products will be made available to buy to promote responsible drinking habits, officials said.

This replaces previous guidelines which allowed sailors to have two cans of beer per day, equivalent to over three units a day, depending on the strength of beer.

The changes also match the navy's goal of improving warfighting readiness when personnel are at sea and line up with guidelines given to the UK's general population, officials said.

"The updated policy aligns with advice from the UK chief medical officer, ensuring that our people remain fit for naval operations and comparable with modern military and civilian maritime standards," a Royal Navy spokesperson said.

"It also prioritises the health of our people, which is paramount, and ensures they are ready to respond to the dynamic demands of naval operations, while also continuing to enjoy downtime."

The new restrictions will not apply when sailors are not aboard ships, for example on on-shore bases, the defence source said.