The world is at its most dangerous point for 40 years, the head of MI6 has warned, accusing Russia of waging a “staggeringly reckless campaign” of sabotage in Europe to undermine support for Ukraine.

Sir Richard Moore also said the West could face a “reckoning” as potential terrorists are radicalised over war in the Middle East.

“In 37 years in the intelligence profession I’ve never seen the world in a more dangerous state. And the impact on Europe, our shared European home, could hardly be more serious,” Sir Richard said, adding that if “Putin is allowed to succeed in reducing Ukraine to a vassal state he will not stop there”.

Sir Richard said MI6 “cherishes our heritage of covert action, which we keep alive today” – with British spies working to stop the consequences of Russia’s invasion of Ukraine. He warned that a victory for Mr Putin in Ukraine would jeapordise both European and transatlantic security, in what appeared a message to president-elect Donald Trump, with the incoming US leader having repeatedly complained about the amount of money and military aid Washington is sending to help Kyiv.

“We have recently uncovered a staggeringly reckless campaign of Russian sabotage in Europe, even as Putin and his acolytes resort to nuclear sabre-rattling to sow fear about the consequences of aiding Ukraine,” he said. “The cost of supporting Ukraine is well known but the cost of not doing so would be infinitely higher. If Putin succeeds China would weigh the implications, North Korea would be emboldened and Iran would become still more dangerous,” he added.

“Our security – British, French, European and transatlantic – will be jeopardised,” Sir Richard said during an event with his French counterpart to mark 120 years since the Entente Cordiale, the Anglo-French diplomatic agreement, was first signed.

The spymaster said his agency and its French counterpart, run by Nicolas Lerner, were working together to prevent a dangerous escalation by “calibrating the risk and informing the decisions of our respective governments” in response to President Putin’s “mix of bluster and aggression”.

Western officials have linked Moscow to several planned attacks in Europe in recent months, including an alleged plot to burn down Ukrainian-owned businesses in London, and to incendiary devices in packages on cargo planes. In July, one caught fire at a courier hub in Germany and another ignited in a warehouse in England.

Moscow has denied responsibility for all such incidents. Sir Richard’s remarks come after Ken McCallum, the head of the UK’s domestic intelligence service MI5, warned last month that Russian spies were on “a sustained mission to generate mayhem on British and European streets” – including “arson, sabotage and more dangerous actions conducted with increasing recklessness”.

Describing British intelligence officials as facing a “hell of a job”, Mr McCallum said both Russia and Iran had turned to employing private intelligence officers and criminals from both the UK and third countries.

Speaking on Friday, Mr Lerner, head of France‘s foreign spy agency DGSE, said that Britain’s experience in the wake of recent attacks like the Salisbury novichok poisoning in 2018 was invaluable to French intelligence officers seeking to defuse Russian actions.

Britain and France have been among Ukrainian allies most willing to allow Kyiv to use weapons they supply to hit certain targets inside Russia, after US president Joe Biden this month eased its long-held opposition to US-made ATACMS missiles being used to do so.

Since then, Russia has bombarded Ukraine’s energy infrastructure with hundreds of missiles and drones, fired and threatened the West with a new intermediate-range ballistic missile, and altered Russia’s nuclear doctrine to lower the threshold for using such weapons.

While Mr Trump’s stance on Ukraine has raised concerns among some UK officials, Sir Richard – who has been mentioned as a possible choice for the UK’s ambassador to Washington – said he was confident the transatlantic bond remained strong.

“For decades the US-UK intelligence alliance has made our societies safer,” he said. “I worked successfully with the first Trump administration to advance our shared security and look forward to doing so again.”

Sir Richard also directly addressed defence spending, with Mr Trump having called on Nato nations to spend more during his first term in the White House. “We know that we all need to do more,” he said. “That’s why the British government has committed to spending 2.5 per cent of GDP on defence.”

However, the MI6 chief said Europe and North America already “have many times Russia’s GDP and defence budget”, adding: “We should never doubt that our alliance has strength in numbers, both economic and military, and our unity of purpose makes that count.”

Turning his attention to the war in Gaza, Sir Richard said: “We have yet to have a full reckoning with the radicalising impact of the fighting and terrible loss of innocent life in the Middle East after the horrors of 7 October.”

The war in Gaza – along with cross-border fire between Israel and Hezbollah in Lebanon – was triggered on 7 October last year, when Hamas launched an attack inside Israel. The militant group killed around 1,200 people and took some 250 hostages into Gaza.

In response, Israel launched a devastating air and ground offensive against Hamas, and Israeli prime minister Benjamin Netanyahu has vowed to keep fighting until all of the hostages are freed. Some 100 hostages remain, although about a third of those are believed to be dead. More than 44,000 Palestinians have been killed in the largely devastated Gaza Strip, according to local health officials, while around 90 per cent of the population of around 2.3 million have been forced from their homes.

The former head of MI6, Sir John Sawers, warned last month that police and intelligence agencies in Britain should be “on their toes” as the assassination of Hamas and Hezbollah leaders by Israel could trigger attacks on British soil.

Additional reporting by agencies