The Russian threats to Britain and Britons are “no longer theoretical”, a former NATO chief said in a chilling warning.

Lord George Robertson, who served as the 10th Secretary General of NATO between 1999 and 2003, slammed the “depraved conduct” of Vladimir Putin‘s soldiers in Ukraine as he vividly portrayed “what the stakes are” in today’s increasingly dangerous world.

Lord Robertson, who is leading the “root and branch” review of the UK’s Armed Forces launched by Prime Minister Sir Keir Starmer, told the House of Lords on Thursday: “We need to recognise… that the threats to our country and our citizens are no longer theoretical. They are no longer a distant possibility.

“They are alive and well in Ukraine today, where Vladimir Putin‘s Russia has brutally invaded and sought to occupy a peaceful, neighbouring independent nation-state.

“Anybody who needs reminding of what the stakes are in the world today need only look at the depraved conduct of Putin’s occupiers in those parts of the Donbas and Crimea that they presently and temporarily occupy.”

World War 3 fears erupted in the wake of the illegal invasion of Ukraine ordered by Putin.

Two and a half years into the war, the Russian threat is affecting the whole of Europe, with Moscow accused of carrying out hybrid and disruptive operations in countries supporting Kyiv’s right to defend its territory.

Many NATO members on the eastern flank have ramped up their defence spending or military preparations to be better equipped for a potential clash with Russia.

The UK has been invited to do the same by Lord Jock Stirrup, who during a debate on military readiness in the Lords said Britain should boost its defence spending as Putin would “not wait upon our pleasure”.

He said: “Dear Vladimir, we know that you’re a dire threat to the peace and security of Europe, but would you mind holding off until we get the books straight?’ I doubt that he would pay attention.”

Russia announced last year it was set to spend in 2024 six percent of its GDP on the military and defence, suggesting it was planning for a long war in Ukraine.