MPs say the police watchdog, the IPCC, should be investigating the "plebgate" affair, which involves former Gedling MP Andrew Mitchell.
Mr Mitchell quit his cabinet post as chief whip following a row over claims he called police officers "plebs".
MP for Leicester East, Keith Vaz, who chairs the Home Affairs Select Committee, says the case shouldn't have been referred to another police force to investigate.
A report out today says David Cameron brought in the the wrong person to investigate 'Plebgate'.
Andrew Mitchell has written a piece in which he has accused the police of trying to destroy his career in a smear campaign.
A police officer who claimed to have witnessed Andrew Mitchell's 'rant' at Downing Street is being investigated by the police watchdog.