Healey said Yantar was currently in the North Sea, after passing near UK waters and being detected 45 miles off the British coast in the English Channel on Monday.

“For the last two days the Royal Navy has deployed HMS Somerset and HMS Tyne to monitor the vessel every minute through our waters,” he said.

“I changed the Royal Navy’s rules of engagement so that our warships can get closer and better track the Yantar. So far, the ship has complied with international rules of navigation.”

The defence secretary said it was the second time the vessel had entered British waters in recent months, with Yantar also detected “loitering over UK critical undersea infrastructure” in November.

He said a Royal Navy submarine had been authorised to surface close to Yantar – a highly unusual move.

Healey described this “strictly as a deterrent measure” and “to make clear that we have been covertly monitoring its every move”.

Defence sources told the BBC the ship was also given a verbal warning.

“The ship then left UK waters without further loitering and sailed down to the Mediterranean,” Healey added.