Britain faces being dragged back into a Cold War with Russia which poses the “single greatest threat to our security”, warns Foreign Secretary Philip Hammond.

He believes that Russia’s intensive beefing up of its military capability was a “cause for concern”, comparing it to a Cold War move.

Russia Is 'Single Greatest Threat To The UK'

In his speech to the London Royal United Services Institute (RUSI) on Tuesday morning, Hammond said:  “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 states are all significant causes of concern”.

His speech comes after Defense Secretary Michael Fallon expressed his concern last month that there was a “real and present danger” in the Baltics and that the Russian President Vladimir Putin could try to destabilize the Baltic states Lithuania, Latvia and Estonia, all of which, unlike Ukraine, are members of NATO.

Mr. Hammond said: “President Putin’s actions – illegally annexing Crimea and using Russian troops to destabilise eastern Ukraine – undermine the security of sovereign nations of Eastern Europe”.

Hammond, who is responsible for Britain’s MI6 overseas spy agency, also said that Putin had decisively rejected efforts to draw his country into a “rules-based” international order and was now actively seeking to subvert it.

“We are in familiar territory for anyone over the age of about 50, with Russia’s aggressive behavior a stark reminder it has the potential to pose the single greatest threat to our security,” Hammond said in his speech in London.

Russia and had caught the West napping

He added that in the face of the “increasingly aggressive” stance of the Russian military, the effort to establish its intentions was now once again a “vital” element of the work of Britain’s intelligence agencies – MI5, MI6 and GCHQ. He called for a need for the UK to continue gathering intelligence about Russia’s “capabilities and intentions” for “the foreseeable future”.

Russia Is 'Single Greatest Threat To The UK'

“It is no coincidence that all of our agencies are recruiting Russian speakers again,” Hammond said.

He emphasized on the necessity of British security agencies to continue their clandestine work. “We must respond decisively and positively to the public and parliamentary debate about the powers required by our intelligence agencies to do their job in a changed technological environment – and in doing so draw a line under that debate so that the agencies can get on with the job of keeping this country safe,” he said.

However, ex-Army chief General Peter Wall had earlier warned that defense cuts have left the UK unable to deal with Russia’s “interference in our airspace and offshore waters”. The former head of the British Army said the 10% cut in defense spending since 2010 has left the UK vulnerable to the threat of Russia and the Islamic State (ISIS). General also claimed that the increased threat from Russia and ISIS had caught the West napping.

During a Q&A session after his speech in London, Philip Hammond hinted at the possibility of Western powers seeking to expose public the private financial operations of top regime figures outside the country in order to catch them off guard in front of their own people. “It is a very interesting thought,” he said.

EU will respond immediately if there is a significant breach of the ceasefire

Later, speaking before the Commons Foreign Affairs Committee, Hammond said that Britain should be prepared to start supplying weapons to the Ukrainians if their military forces start “crumbling” against the Russian-backed separatist rebels.

Hammond also commented on the Government’s decision to restrict its aid to Kyiv to non-lethal equipment, by saying: “We want to keep our options open here but we don’t believe there is a military solution to this conflict and we are very wary of giving the mis-impression that we perhaps do think that if we were to focus on supplying lethal equipment to the Ukrainians,” he said. “But equally, we can’t afford to see the Ukrainian armed forces crumble”.

However, he warned that any further escalation of the conflict by the separatists would result in a new round of European sanctions against Moscow. “There is a very clear acceptance across the European Union …. that if there is a significant breach of the ceasefire – a major assault for example on Mariupol – the European Union would have to respond and respond immediately with a significantly increased regime of sanctions”.

Russia Is 'Single Greatest Threat To The UK'

He stressed that the Government fully understood the concerns about the situation in the Baltic states, and the fact that they could be Putin’s next target, and he made clear that the convention that ministers should consult Parliament on military action did not mean it could not act while Parliament was dissolved for the general election. “In no circumstances would it be right to postpone military intervention that was required for the safety and security of Britain or the alliance because we were unable to consult Parliament because it was dissolved at the time,” he said. “It would require the government to bring that issue to Parliament as soon as the new Parliament was formed for what would be retrospective endorsement”.

Earlier, speaking on Monday, Deputy Prime Minister Nick Clegg said that the Conservative party had to “come clean” on the military budget, arguing that they cannot shrink the state and also “somehow pretend that they can fund everything in sight”.

“You cannot provide the British people with adequately resourced police forces, or an adequately resourced military forces if you take this ideological approach to reducing the amount of money that goes into public spending as a proportion of GDP for no economic reason at all.”

He added: “At some point, the Conservative Party has got to come clean. They cannot have their cake and eat it. They cannot embark on this rightwing lurch towards an ever-shrinking state and also somehow pretend that they can fund everything in sight. You can’t. Something has to give.”

There has been an increasing pressure on the government from former NATO chiefs and senior defense officials to commit to the NATO target of spending 2% of GDP on defense beyond 2016.