A new breed of “super-quiet” Russian submarines are feared to be operating unseen in British territorial waters, according to military sources.

The new Russian Kilo-Class submarines are feared to be threatening UK security by tracking Britain’s fleet in the North Atlantic undetected or by tapping into under-sea internet cables.

HMS Queen Elizabeth, the Royal Navy’s flagship aircraft carrier, and the nation’s nuclear deterrent submarines could be vulnerable to the Russian boats' stealth technology, extended combat range and ability to strike targets above and below the water as well as on land.

“The new First Sea Lord needs to deliver the underwater battle,” a senior military source told the Telegraph. “We must be better at what we do.”

“The Russians are benefiting from a huge increase in research and development spending 15 to 20 years ago which is now producing this new class of super-quiet Kilo Submarines.”