London: British Foreign Secretary on Tuesday warned that Russia could pose the "single greatest threat" to the UK and indicated that the West needed to scale up their intelligence services to check President Vladimir Putin's aggressive behaviour.
"We are now faced with a Russian leader bent not on joining the international rules-based system which keeps the peace between nations, but on subverting it," said Philip Hammond.
He said: "We are in familiar territory for anyone over the age of about 50, with Russia's aggressive behaviour a stark reminder it has the potential?to pose the single greatest threat to our security."
Hammond said Putin's actions in Crimea and eastern Ukraine "fundamentally undermine" the security of eastern European states.
In a speech at the Royal United Services Institute (RUSI), Hammond said for two decades since the end of the Cold War Britain has worked in a spirit of openness, generosity and partnership, to help Russia take its rightful place.
Hammond, who is the also minister responsible for Britain's MI6 foreign spy service, said it was a major power contribution to global stability and order.
"We now have to accept that those efforts have been rebuffed," he said. "It is no coincidence that all of our agencies are recruiting Russian speakers again."
"The rapid pace with which Russia is seeking to modernise her military forces and weapons, combined with the increasingly aggressive stance of the Russian military, including Russian aircraft around the sovereign airspace of NATO members states, are all significant causes for concern," he said.
Russia denies Western accusations that it backs the separatists fighting against government forces in eastern Ukraine.
Putin has, however, acknowledged ordering the annexation of Crimea from Ukraine last year, sparking international condemnation.