A North Wales Police officer, three from Greater Manchester and a Cheshire officer have now resigned after a secretly-filmed BBC documentary on racism.
Pulling was filmed wearing an improvised Ku Klux Klan mask
The first to go, Robert Pulling, was described as "a disgrace" by North Wales' Deputy Chief Constable Clive Wolfendale.
The departure of the three Greater Manchester officers and the officer from Cheshire was confirmed later on Wednesday.
Three other policemen - one from North Wales, two from Greater Manchester - have been suspended.
The North Wales force called a media conference to discuss the BBC documentary, The Secret Policeman, which filmed Mr Pulling's overt racist comments while he was both training and at work in Wales.
He defended the force's record on fighting racism after the programme, screened on Tuesday, which led to eight officers - two in Wales - being suspended.
The programme, The Secret Policeman, showed trainee officers expressing hostility towards an Asian recruit, who is now serving in the north Wales force.
Pc Rob Pulling worked in the force's central division, which covers towns like Rhyl, Colwyn Bay and Llandudno.
Clive Wolfendale said he felt sick watching the programme
He was suspended pending a North Wales Police investigation prior to the programme's screening.
The second officer suspended was Pc Keith Cheshire.
Pc Pulling was asked by undercover reporter Mark Daly during the filming if he was capable of killing an Asian man. He replied: "I've got it in me... it's a hatred thing."
Mr Pulling and others were heard criticising the only Asian recruit in the intake.
When the man was required to retake some of the course, a number of the trainees were heard to cheer.
North Wales Police stressed it had been working hard to tackle racism within its own ranks.
Mr Wolfendale described the men in the footage as "a group of racist delinquents".
He said Chief Constable Richard Brunstrom would be writing to the family of murdered black teenager Stephen Lawrence to apologise for comments made in the film about the family and the tragedy they have suffered.
He said: "I felt physically sick as I watched The Secret Policeman last night.
Rob Pulling has resigned from North Wales Police
"Robert Pulling was a raw recruit who had never walked the streets unsupervised, or dealt with an incident unchecked.
"He had not finished training, nor been exposed to the prevalent culture of North Wales Police. But all of that is scant comfort.
"Pulling has shamed his colleagues, his uniform, and the service. He is a disgrace."
He said he believed society was now more racist that it was five years ago,
citing "national and international reasons" but added: "We are determined to
deal with the consequences."
'Surprised and saddened'
He concluded by saying: "There's no place for racism in North Wales Police.
Malcolm King, chairman of North Wales Police Authority, said: "Clearly we need to learn from what has happened and drive out any vestiges of racism that remain in North Wales Police."
The Asian officer shown in the film as the target of racist comments made an anonymous statement which was read out at the media conference.
He said: "I am surprised and saddened at the behaviour and comments made by a small number of officers towards me.
"I am proud to be a North Wales Police officer and have received tremendous support from the force and my colleagues.
"I remain committed to being a police officer and serving the communities of north Wales."