Britain's top policeman has warned: "I will not stand for any racism or racists" as he vowed to get to the bottom of "very damaging" allegations against his force.

Metropolitan Police Commissioner Bernard Hogan-Howe spoke out after footage emerged of one officer apparently racially abusing a man and another allegedly assaulting a teenage boy last summer.

In a statement to staff, the police chief said: "I wanted to take this opportunity to clearly and categorically reiterate that there is no place for racism in the Met."

Both incidents happened on August 11 last year as police officers in London dealt with the fallout of the riots sweeping the capital.

In an internal broadcast to staff, Mr Hogan-Howe said: "I know that the Met has changed greatly over the years, and most of you have directly been involved in improving our relationship with all Londoners and those who visit us.

"Unfortunately just one alleged incident like this can be very damaging to public confidence."

Pc Alex MacFarlane of the Metropolitan Police has been suspended after a recording was made of a suspect being called a racist term.

The arrested man, named as Mauro Demetrio, 21, from Beckton, east London, was arrested on suspicion of drug driving but no action was later taken. He recorded the abuse on his mobile phone.

It later emerged that another officer, reportedly with Pc MacFarlane when Mr Demetrio was abused, was placed on restricted duties after being allegedly seen kicking the 15-year-old black boy to the ground and kneeing him.

The incident was said to have happened in the custody area of an east London police station with part of the incident recorded on CCTV.