Scotland Yard is investigating after former prime minister David Cameron’s bodyguard reportedly left his gun in an aeroplane toilet.

The weapon was found by a passenger, who handed it to flight attendants on a transatlantic flight from New York to London, according to the Daily Mail.

The gun, believed to be a 9mm Glock 17 pistol, is said to have been left by a close-protection officer who took off his holster while using the toilet.

Passports belonging to Cameron and the officer were also found alongside the weapon, according to the Sun.

In a statement, the Metropolitan Police said: “We are aware of the incident on a flight into the UK on February 3 and the officer involved has since been removed from operational duties.

“We are taking this matter extremely seriously and an internal investigation is taking place.”

Cameron, as a former prime minister, is entitled to continued security provided by the Met’s specialist protection unit.

A BA spokesperson said: “We follow CAA rules which allow UK police to carry firearms on board in specific, controlled circumstances.

“Our crew dealt with the issue quickly before departure and the flight continued as normal.”