The Queen of England's security could be at risk from serial squatters who invaded a building metres away from Buckingham Palace, the property's owners have claimed.

Around a dozen activists moved into the seven-storey property on Buckingham Gate, in the shadow of the British monarch's residence, rebranding it the Rogue Embassy.

Court documents shown to the Press Association by the squatters cited a Metropolitan Police royal specialist protection officer who flagged a "potential security risk" posed by the group.

Concerns were raised that, if the occupiers accessed the adjoining roof, they could directly peer into the gardens of the royal grounds.

But one of the protesters insisted they were not "going to do anything".

A witness statement filed to the High Court by Archie Riby-Williams, a director of owning company 18-19 Buckingham Gate Investments Limited said: "At around 10.30am on February 23, I spoke with...a royal specialist protection officer at Buckingham Palace who expressed his concern about the potential security risk to the Palace if the defendants gained access via the roof of the premises 18 and then 17 Buckingham Gate.

A banner reading "Rogue Embassy" hangs outside 19 Buckingham Gate, London, which has been squatted by the Autonomous Nation of Anarchist Libertarians. Pic: PA

"If the defendants were to access the roof of 18 Buckingham Gate in particular, this would enable them to see directly into the garden of Buckingham Palace and this would, in fact, appear to be the defendants' objectives."

Snipers stationed on the roof of Wellington Barracks were in "regular contact" with a next-door owner to raise concerns about the view into the palace gardens from the roof, the document said.

The occupiers claim to be part of the Autonomous Nation of Anarchist Libertarians and said they expected eviction efforts to begin on Friday night.

It is the third high-profile building the band of squatters have entered this year.

They were evicted from a multimillion-pound property in Eaton Square, central London last month, before immediately moving into a nearby seven-storey building on Grosvenor Gardens.

The once-lavish property on Buckingham Gate, which neighbours the Swaziland High Commission, has been adorned with flags and banners by its new occupants.

Owned by Bahraini Abdulrahman Aljasmi, it has stood derelict for decades, the group claimed, leading them to repurpose it as an embassy for "indigenous people" and "nations that are not recognised".

One of the activists said: "It is a very high-profile building. As a sport, it is an achievement even having a squat for a couple of days.

"It is an achievement to get as near as we can to Buckingham Palace, not that we are going to do anything.

"It is theatre for us, it is confrontation theatre."

Another added they intended to move from "building to building" throughout London.

A Buckingham Palace spokeswoman said: "We never comment on security, which is a matter for the police."