A police force is at the centre of a corruption inquiry over claims that officers conspired with the boss of a Labour council to lock up critics and acted as her “private enforcement agency”.

Greater Manchester police’s professional standards department has begun an investigation into allegations that at least four outspoken present or former councillors in Wigan were wrongly arrested by officers after complaints from Donna Hall, chief executive of Wigan council at the time.

Operation Floret will look at claims of an “inappropriate relationship” between the force and the local Labour Party amid claims that riot police were used to arrest political opponents.

The force is accused of denying basic rights to a politician who was arrested by seven officers and held in a