BBC reporter Mark Daly exposed racism

A GMP spokeswoman said the probationary officer, based in Cheadle Hulme, was "forced to resign" after a disciplinary hearing.

It brings to six the total number of GMP officers who have quit over the revelations in the BBC documentary The Secret Policeman.

The 31-year-old officer, who has not been named, was seen to make racist remarks in unbroadcast footage.

In a statement on the GMP website, chief constable Michael Todd said he will not tolerate racism in his force.

'Public faith'

"Officers who believe that they can survive in my force whilst behaving in an overtly racist manner are deluding themselves - they cannot and will not," he said.

"It is a small number of people who let us down.

"However, the impact of their behaviour is extremely damaging to the service we provide and the public's faith in our ability to deliver with equal respect to all.

"Overcoming this is a serious challenge not only to me as a chief constable, but also to all ranks of officers and staff and indeed society as a whole.

"However, it is a challenge that we recognise, a challenge we take seriously and a challenge that together we are committed to tackling successfully."

Undercover reporter Mark Daly, 28, joined GMP as a trainee officer and secretly filmed recruits at Bruche National Training Centre in Warrington, Cheshire, as well as officers on the beat.

He was originally arrested, but will not now face charges.