Fears have been raised the UK's defences are at risk due to a 'chronic' shortage of 'proper' Royal Navy warships available to shadow Vladimir Putin's naval armada.
Warships, submarines and spy vessels from the Russian leader's fleet have been seen skulking off the coast in the Channel, North Sea and Irish Sea in recent months.
Britain's navy has repeatedly scrambled warships and submarine-hunting helicopters to escort the vessels, in operations defence officials insist are 'routine'.
But increasingly, the navy appears to be relying more on lightly-armed patrol ships instead of its fleet of more powerful frigates and destroyers to carry out the task.
Only half of the nation's fleet of ageing Type 23 frigates - which specialise in seeking out Putin's underwater nuclear boats - are understood to be available.
