A West Yorkshire MP has said the Prime Minister needs to "show some leadership and judgment" over the Andrew Mitchell incident.
Yvette Cooper, Labour's Shadow Home Secretary, said David Cameron should make Mr Mitchell stand down as Chief Whip "straight away".
It follows claims he called police officers "plebs" after they made him wheel his bike out of Downing Street's pedestrian exit instead of opening the main gate.
He has apologised to the officers but has denied using the word "plebs".
Defence Secretary Phillip Hammond said the row had been "hijacked".