Up to 50 Russian spies could now be on the prowl in Britain in the wake of the Ukraine war.
MI5 believes Vladimir Putin has ordered all sleeper agents – under deep cover – to be ready to spring into action.
Spy hunters are already on alert for possible cyber attacks in response to the UK’s support for Ukraine.
And intelligence chiefs fear agents will also attempt to steal our military secrets and target Russian dissidents and Ukrainian activists living here.
Sources claim Putin has spies in all areas of British society, from top public schools to staff in the civil service and the House of Commons.
A senior intelligence insider said: “We have to assume Russia is now active at all levels of British society. They scoop up all forms of intelligence and pass it back to the Kremlin through handlers.
“This could be anything from what sort of weaponry is being sent to the Ukraine – and how much of it – to the sexual antics of the country’s political and military leaders.”
The disclosure comes after a suspected Russian spy was seized at Gatwick last week.
The man in his 40s was held under the Official Secrets Act and remains in custody.
Lt Col Philip Ingram, a former military intelligence officer, said: “It is impossible to accurately assess how many Russian agents there are in the UK.
“Of course there are different types – declared intelligence officers known as part of Russian diplomatic missions, and those operating under cover trying to recruit agents and then sleeper agents in all aspects of society.
"Given our support for Ukraine, Russian intelligence will be focused heavily on operations inside the UK and could also include recruiting agents inside political establishments, defence and industry”.
Last week it emerged up to four Russian spies may have infiltrated the Commons. MP Chris Bryant said there have been no recent warnings to MPs about the presence of Russian agents.
But he said it was likely there were a “handful” of Russian moles inside Parliament.
“If the war is prolonged then I think we will see Russia reverting back to old Cold War-style spying techniques,” Mr Bryant said.
A Home Office spokesman said: “We have made huge strides in recent years to counter the threat posed by the Russian state and to increase our resilience and that of our allies to Russian malign activity.”
