The chair of the House of Commons Home Affairs Committee, Keith Vaz, has said a "robust, transparent and comprehensive investigation" is needed into the 'plebgate' affair.
He suggested it should be carried out by HM Inspectorate of Police or the Independent Police Complaints Commission, rather than the Metropolitan Police.
In a letter, he called on Met Commissioner Bernard Hogan-Howe to provide the committee with an explanation of how information about the Andrew Mitchell altercation got into the public domain and why the Downing Street police log "appears to conflict with CCTV evidence".
Mr Vaz - who said the latest revelations raise "serious issues of concern" - also asked for an explanation of "the actions of the police officer who apparently claimed to provide information about the scene at which he was not present, and how he obtained this information".
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.