Arsenal midfielder Granit Xhaka has been interviewed by police after being accused of racially abusing a member of staff at Heathrow Airport on Monday night – little over 24 hours after he had been sent off in his team’s victory over Burnley.

The incident completed a remarkable sequence of ill-discipline for the Premier League title chasers, with Xhaka already preparing to serve a long suspension and manager Arsene Wenger facing the threat of a touchline or stadium ban for pushing a fourth official.

Xhaka was seeing off a friend, German sixth division footballer Leonard Lekaj, who was refused entry on to a flight to Germany after arriving late for boarding.

A stunned witness claimed the 24-year-old midfielder, who cost Arsenal £32.5 million from German club Borussia Mönchengladbach, racially abused a member of staff by saying ‘f------ white b-----’ in German, at which point airport security and police were called.

Xhaka, who was born in Switzerland to Kosovo Albanian parents, was then cautioned and taken to a west London police station for questioning. He disputes the words he is accused of saying and denies saying anything directly to the member of staff.