Russia's intelligence services have become 'feral' and 'reckless' in the way they are plotting attacks in Britain and across Europe, the head of MI6 warned in a rare public appearance yesterday.

In an historic joint interview with the head of the CIA, Richard Moore said Moscow is now using criminal gangs for state-sponsored terror attacks in Europe, which are endangering more lives as they are 'more amateurish'.

His CIA counterpart William Burns said coordinated operations between UK and US intelligence services are thwarting the plots across the Continent and in mainland Britain. 

They were appearing before a packed audience amid tight security at the FT Weekend Festival in north London, where they spoke of the long-standing relationship between MI6 and the CIA.

Mr Burns also revealed how the CIA feared Vladimir Putin was going to deploy tactical nuclear weapons in Ukraine in the autumn of 2022, after falsely accusing President Volodymyr Zelensky of amassing nuclear materials for such an attack against his troops.

The CIA chief also said 90 per cent of a new peace deal between Israel and Hamas is complete, adding that its details may be published in the 'next few days'.

Mr Moore, known as C by his officers, spoke about how the two services often conduct intelligence operations together. 'We will sometimes decide who is better-placed to go first – we call it the best athlete model. Whoever is best placed to do it, we work in a non-competitive way to get the result,' he said.

The MI6 boss said Russia's intelligence services have conducted sabotage and criminal acts in Britain and in Europe, becoming 'a lot more feral'. 

He added: 'The fact they are using a criminal element shows they are becoming a bit desperate – they can't use their own people. They're happy to use criminals. It's just a bit more reckless.'

In April, an alleged arson attack was carried in Leyton, East London, on a Ukrainian-linked business, which was suspected of being directed by Moscow. Seven men have been charged in relation to the incident, with two under the new National Security Act. 

Mr Moore said the Salisbury poisoning in 2018 was ‘emblematic’ of the recklessness of Russian agents. 

'They left a large phial of a deadly poison lying around to be picked up,' he said. 'It could have killed an entire school – in fact, it killed an innocent British civilian.'

Two Russian agents daubed Novichok nerve agent on the door knob of former Russian spy Sergei Skripal, which nearly killed him and his daughter. But the perfume bottle with the poison in it was later picked up by a woman called Dawn Sturgess, who later died.

Speaking publicly for the first time about how the CIA feared Russia was close to using a tactical nuclear weapon in Ukraine months into the conflict, Mr Burns said: 'There was a moment in the fall of 2022 that I think there was a genuine risk of potential use of tactical nuclear weapons. I felt we should not be intimidated by Putin.'

He was dispatched to the Turkish capital Ankara to tell the head of the FSB, Sergei Naryshkin, how the West would respond 'militarily' if Russia used nuclear weapons in Ukraine. 

Mr Burns said yesterday: 'We cannot afford to be intimidated by that sabre-rattling and bullying. The record shows the United States has provided enormous support to Ukraine, and I'm sure we'll continue to.'

Mr Burns has been intimately involved in the difficult negotiations in the Middle East between Hamas and Israel, with Qatar and Egypt acting as intermediaries.

He said 90 per cent of a peace deal is complete, adding: 'The last 10 per cent is the last 10 per cent for a reason... it's the hardest part to do. But we will make this more detailed proposal, I hope in the next several days, then we'll see.'

And he warned that Hamas cannot be entirely defeated. 'Hamas is a despicable terrorist organisation,' he said. 'You can severely degrade their military capabilities, but it is a movement and an idea, and the way you kill an idea is with a better idea.'

The intelligence chiefs – who gave a public interview to Financial Times editor Roula Khalaf on the grounds of Kenwood House in Hampstead – said China was their main preoccupation, with 20 per cent of the CIA's resources being devoted to the Beijing regime.