Andrew Mitchell, who lost his job over claims he called police officers in Downing Street 'plebs', says the allegations were a deliberate attempt to ruin his career.
The former chief whip also said the smears were designed to damage the Conservative Party.
Today the head of Scotland Yard has promised a "ruthless" search for the truth.
Political Correspondent Alex Forrest reports:
Britain's most senior police officer has promised a "ruthless" investigation into an alleged conspiracy against Andrew Mitchell.
Andrew Mitchell has written a piece in which he has accused the police of trying to destroy his career in a smear campaign.
Police investigating the row involving Andrew Mitchell have arrested a second man today. See how the "plebgate" events unfolded.