Russia is becoming more aggressive on British soil, the Chief of Defence Staff has warned.

Admiral Sir Tony Radakin, head of the British military, said that while the world's rules-based international system is under strain, most keenly felt in Ukraine as a result of Vladimir Putin's illegal invasion, the UK is not without threat.

Sir Tony said: "Increasingly the challenge is also being felt in this country. Six years ago, British citizens were poisoned by a chemical attack on home soil. Since then, our airspace and sovereign waters, our critical energy and digital infrastructure and our public realm have been subject to interference."

His comments, made to mark Remembrance Sunday - a moment to honour those who died while fighting for their country - come after Ken McCallum, the director general of MI5, warned that Russian spies were targeting Britain in Cold War-style espionage.

He said that this included Putin's intelligence agencies targeting businesses to undermine the UK's security and economy.

Mr McCallum warned that as the Ukraine war "grinds on" Russian state-sponsored sabotage attempts targeting UK businesses, as well as going after government and military secrets, were being acted out in order to "generate mayhem in British streets".

Writing in The Times, Sir Tony said: "There are good reasons to be confident, including our status as a nuclear power, the collective strength of Nato, our wealth as a G7 economy, extraordinary new military-industrial alliances like Aukus and the outstanding quality of our servicemen and women.

"But the challenges we are experiencing are not bumps in the road. This is a new era of competition and contest that will last for decades and has the potential to be more disruptive to our economy and our security than anything Britain has experienced in modern times."

He added that the response to these threats "requires us to leverage not just our military capabilities, but our industrial strength, our technological and scientific base and our national wealth and most importantly our allies and partners".

Sir Tony added that it was "sobering" to visit Ukrainian recruits doing their infantry training in the UK, stressing that they are men in their 30s and 40s who came from ordinary jobs and left behind families, wives and children, to learn how to fight.

"Now they are marching off to war, to free their country and defend their families from the most barbarous acts of aggression," he said.

It comes after John Healey, the Defence Secretary, told The Telegraph that Europe was "undoubtedly in an era of insecurity".

"It weighs heavily on me as Defence Secretary, knowing that if we face conflict, it will be my decision to send British forces and personnel into situations which puts them at risk," he said, cautioning that "the West can and must" put an end to Putin's war in Ukraine.