Counter-terror police are investigating whether a hostile state was involved in the arson attacks on Keir Starmer’s home – as his family say they have been left ‘frightened’.

A 21-year-old man is accused of setting the Prime Minister’s £2m north London property alight on Monday night, just days after the torching of a car and a flat which he had previously owned.

The head of Counter Terrorism Command issued a statement urging any MPs who may be concerned to contact police, with police sources saying they have an open mind as to the motive.

Sir Keir has let the four-bedroom house in Kentish Town to his sister-in-law on a peppercorn rent since he moved into Downing Street last year.

City mayor Sir Sadiq Khan said the three arson attacks had left the Prime Minister’s family feeling ‘frightened’ for their safety.

He told LBC Radio: ‘Don’t underestimate the ripples of fear that [his wife] Vic and the kids felt when they will have read this stuff in the paper.

‘But for the grace of God they are safe thankfully, in Downing Street, they’ve got a protection team.

‘But they will have felt scared, frightened… It can’t be right that any politician and their family faces these sorts of threats. And the context is that in the last ten years we’ve had two politicians losing their lives in this country, David Amess and Jo Cox.’

FIRE ONE: Exclusive MailOnline footage shows the dark blue Toyota Rav 4 engulfed in flames as firefighters fought the blaze on VE Day last Thursday

FIRE TWO: Scotland Yard is also probing another blaze at another property in north London linked to the Starmer just 24 hours earlier (pictured), on Sunday

FIRE THREE: The front door and brickwork at Sir Keir Starmer’s north London townhouse has been left charred following a suspected arson attack in the early hours of Monday morning

No one was hurt in the attacks between May 8 and May 12, but police believe the culprit ‘intended to endanger life’.

The motive has not yet been established, but counter terrorism officers are pursuing several theories, including whether a fixated individual bore a personal grudge and the possibility of involvement by a hostile state.

A source said the indications were that the alleged plot showed a degree of ‘sophistication’.

Commander Dominic Murphy said: ‘We are working at pace and continue to explore various lines of enquiry to establish the cause of the fires, and any potential motivation for these.

‘A key line of enquiry is whether the fires are linked, due to the two premises and the vehicle all having previous links to the same high-profile public figure.

‘We recognise that this investigation may cause concern to other public figures, particularly MPs.

‘The protection of MPs is something we take extremely seriously across the whole of policing and I would encourage any MP who is concerned about their own safety to get in touch with their dedicated local Operation Bridger officer, who can provide further advice and support.’

The motive has not yet been established, but counter terrorism officers are pursuing several theories

The torched remains of the 4×4 after the fire last week

The owner of the car initially thought it was a battery fault. Now counter-terrorism are involved due to fires linked to the PM. A man, 21, has been arrested

Detectives enter Sir Keir Starmer’s fire damaged home

Sir Keir and his wife, Victoria, were previously seen clapping for the NHS from outside the home in London, during the height pandemic in May, 2020

Tory leader Kemi Badenoch said: ‘My thoughts are with the Prime Minister and his family. No one should face these sorts of threats…It’s an attack on our democracy and must never be tolerated.’

Last Thursday, Sir Keir’s old Toyota Rav4, which was parked outside the Kentish Town property, was torched.

One neighbour, former dinner lady Linda Perry, 80, said: ‘At 3am I woke up to the sound of people screaming “fire, fire” and the sky outside was lit up.’

Three days later the front door of a flat in Islington which Sir Keir owned between 1991 and 1997 was doused in an accelerant.

Last night police were quizzing a 21-year-old man arrested in south London on suspicion of arson with intent to endanger life.

It comes as last year Assistant Commissioner Matt Jukes, the head of UK counter terror, warned the number of investigations involving hostile states, such as Russia and Iran, had quadrupled in recent years.