More than 20 police officers responsible for protecting the royal family have been placed on ​restricted duties after some were accused of falling ‌asleep at Windsor Castle and leaving their posts unattended, London police said.

A total of 23 officers from the Royalty and ​Specialist Protection command have been served with ​misconduct notices, with 21 of them on restricted ⁠duties, following what the force described as an urgent ​investigation launched last month, the Metropolitan Police said.

“The alleged ​behaviour falls below the high standards expected of officers, particularly in frontline protective roles,” a spokesperson for the force said.

The ​allegations came to light after the Sun newspaper reported ​that officers were accused of leaving their posts unattended at Windsor, ‌one ⁠of King Charles’ residences, as well as sleeping while on duty.

Officers from the police specialist unit are responsible for protecting members of the Royal Family and ​guarding royal residences.

The ​two officers ⁠not placed on restricted duties would not be deployed to royal residences while ​the investigation continued, the police statement said, ​adding ⁠that enquiries were also under way at other royal residences.

Windsor Castle, where the king hosted US President Donald Trump last ⁠year ​to the west of London, ​is regularly used for both private stays and state occasions.

Buckingham Palace declined ​to comment.