Britain’s nuclear submarines are outnumbered by Russian vessels flooding into the North Atlantic, while Vladimir Putin has reopened a cruise missile base within range of UK targets, The Mail on Sunday has learned.

The terrifying surge by Russian subs into waters previously controlled by the Royal and US navies is part of a provocative new Cold War strategy by Moscow, say military experts.

Last night, the head of the Royal Navy, First Sea Lord Admiral Tony Radakin, confirmed that Russia is ‘more active in the Atlantic – our backyard – than it has been for over 30 years’. And he warned that China could soon pose a threat to British waters.

Naval sources report the upsurge involves Russian Akula-class submarines, equipped with the latest stealth technology, sailing close to the UK’s coast.

The new threat comes as Russia appears ready to resume the testing of nuclear-powered cruise missiles capable of reaching Britain at a previously dismantled launch site near the Arctic Circle.

A source said: ‘The sheer number of Russian submarines entering the North Atlantic is overwhelming.

‘The tactics adopted by their captains are deliberately provocative and highly dangerous.

‘While our Astute-class submarines sailing from Faslane in Scotland are a match for their best submarines, the Russians are sometimes deploying two or three submarines into our areas of operations where previously they would have sent only one.

‘The war-gaming and manoeuvring has never been more intense, especially when we are unable to precisely locate our enemies. The situation is serious and must be addressed by the Government before it is too late.’

The current hotspot is a stretch of water between Greenland, Iceland and the UK called the GIUK Gap. A strategically significant passage, it is a choke-point for submarines where they can be identified by other navies. Alarmingly, the latest generation of Russian submarines can apparently pass through the Gap undetected before heading towards Britain.

Rear Admiral Chris Parry said: ‘We face a stark choice. If Britain is to be protected in any future conflict, there will need to be substantial investment in our anti-submarine technologies and skills. We have catching up to do.’

It comes as US academics studying satellite imagery report that Russia is preparing to use a test base for advanced nuclear-powered weapons at a site known as Pankovo, after recently recording high levels of activity there.

Warning of another potential threat, Admiral Radakin said that the shrinking of the polar ice cap by global warming could allow Chinese submarines easier access to our waters.

‘When China sails its growing navy into the Atlantic, which way will it come – the long route, or the short?’ he said. ‘These routes skirt the coast of that resurgent Russia.’