Scotland Yard is facing a racism scandal after a black man used his mobile phone to record police officers subjecting him to a tirade of abuse in which he was told: “The problem with you is you will always be a nigger”.

The recording, obtained by the Guardian, was made by the 21-year-old after he was stopped in his car, arrested and placed in a police van the day after last summer’s riots.

The CPS initially said charges should not be brought against MacFarlane because the remarks did not cause the man harassment, distress or alarm.  However on Thursday, the service said it would review the file after lawyers for the man threatened to challenge the decision in a high court judicial review. MacFarlane has been suspended.