Sunak left for a 10-day family holiday in California on Wednesday so neither he nor his relatives were not in his £2 million mansion in Richmond, North Yorkshire at the time.
Still, eyebrows have been raised after four Greenpeace activists climbed up 40ft, and covered his home in a 200 sq metre black fabric.
It was a protest against the PM’s decision to award 100 more licences for drilling for oil and gas in the North Sea.
Two protesters also held a banner with the words ‘Rishi Sunak – Oil Profits or Our Future?’ in front of the house.
Police were promptly called, and four of the activists were arrested.
However, former North Yorkshire Police deputy chief constable Peter Walker told LBC that the whole incident caused him concern.
He said: “I am absolutely astonished that they have been able to gain the access that they have.
“It is clearly, in my view, a major breach of security.
“Obviously, nobody was there to prevent what they were doing and they’ve had access to the roof as well.”
Walker acknowledged that the protest had not caused any damage, but openly pondered why free access was being granted to the property.
“I think this is a major failing and it grieves me to say it because it’s my old police force that’s failed,” he said. “I suspect that what has happened is that people have not done their job – in an operational sense – who are much closer to the action.
“But there really does need to be a significant investigation into how this has been allowed to happen.”
Greenpeace have defended the move by claiming it was a “peaceful protest” and they knocked on the door to explain themselves when they arrived – only to find there was no answer.
It’s not clear who reported them to the police.
Philip Evans, Greenpeace UK’s climate campaigner, said: “We desperately need our prime minister to be a climate leader, not a climate arsonist.”
He added: “The experts are clear – we can’t afford any new oil and gas, and the fossil fuel industry certainly doesn’t need another helping hand in destroying the climate.”
He claimed Sunak’s suggestion that more locally sourced fossil fuels would cut bills is “not true” because of the government’s generous windfall tax.
He also accused the PM of “sowing division around climate” and called for a “clean, affordable energy system”.