Scotland Yard Pc Alex MacFarlane is to be charged with a racially aggravated public order offence after the alleged abuse of a suspect during the London riots, the Crown Prosecution Service has said.
Alison Saunders, chief prosecutor for London, said she had advised the Independent Police Complaints Commission to charge Pc MacFarlane despite the CPS's decision not to charge him in January.
Saunders said the original CPS decision was "regrettable", adding that a prosecution was necessary to maintain public confidence.
Pc MacFarlane was stripped of his duties in relation to mobile phone footage which appeared to show him telling the 21-year-old black man: “The problem with you is you will always be a n*****, yeah? That’s your problem, yeah.”
Saunders said: "Having now had opportunity to consider all available evidence, including the statements of others in the van alongside the recording, the lawyer reviewing the case concluded that the inconsistencies in the various accounts of what happened were such that no additional charge could properly be added.
The arrested man, named as Mauro Demetrio, 21, from Beckton, east London, was held on suspicion of drug-driving in August last year but no action was later taken.
The charging announcement came as Met Commissioner Bernard Hogan-Howe appeared before MPs over the force's review of racist allegations.
Hogan-Howe said he was pleased that prosecutors had reviewed their original decision.
"We have to let the criminal case take its course," he said, stressing that the claims were still only allegations.
"I'm glad that it will be tested in court."
Ms Saunders said a prosecution was "necessary in order to maintain confidence in the criminal justice system.
"That is the test I must apply under the Code for Crown Prosecutors when reinstituting a prosecution.
"Accordingly, I have advised the Independent Police Complaints Commission to charge Pc MacFarlane.
"It is regrettable that the original decision was wrong, but I hope the action taken and my decision today demonstrates the willingness of the CPS to review its decisions independently and swiftly and to take appropriate action where necessary."
Another allegation of abuse by a police officer against a youth at Forest Gate police station remains under consideration, the CPS said.
The CPS announcement came as the police watchdog announced a review of a string of complaints about racism at the Metropolitan Police, warning of the risks of "much wider disaffection and dissatisfaction" with the force.
Check out the news of the day in pictures below: