A North Wales Police officer is among four who have been suspended over allegations of racism at a police training centre.
It is alleged one officer dressed in a Ku Klux Klan mask
The suspension came after the home secretary called on the force to take action over material in a BBC TV programme.
Called The Secret Policeman, the documentary due to be shown on Tuesday night, was filmed at a police training centre in Warrington, Cheshire.
The north Wales officer was filmed apparently making racist comments by an undercover reporter.
The other three suspended officers work for Greater Manchester Police.
The programme was made by an undercover who spent five months posing as a probationary officer with the Greater Manchester force at their training centre in Warrington in Cheshire.
While there it is alleged he saw an officer wearing a mask similar to those worn by the American white supremacist cult the Ku Klux Klan.
The undercover reporter from the BBC also claimed to have taped racist comments by some officers.
A spokeswoman for Home Secretary David Blunkett said he had asked both the police forces involved to take decisive action over the allegations.
On Monday, North Wales Police Deputy Chief Constable Clive Wolfendale said: "If the BBC has evidence of racist behaviour by a North Wales officer, we would want to act on that immediately.
"There is no place for racists here.
"Even though we have still not seen the programme or had any evidence from the BBC, our internal information is such that we have suspended the officer until the facts and identity are clear."
Greater Manchester Police (GMP) said its officers would be suspended pending an internal investigation and added it would take further action against any other officers shown making racist comments.
Greater Manchester Police Deputy Chief Constable Alan Green said: "We are disappointed that, despite repeated requests, we have not yet received a copy of the programme from the BBC to enable us to take immediate action.
"However, in the light of the information we have received from elsewhere, we have no hesitation in suspending these officers pending a thorough investigation.
"We have always made it clear that any racist behaviour in whatever form will not be tolerated within Greater Manchester Police.
"We will be unrelenting in our actions against racism both inside and outside the Greater Manchester Police service."
The BBC defended its methods, claiming its undercover operation was the only way to bring to light the problem of racism within the police.
In a statement, the BBC said: ""The details of our discussions with senior police officers remain confidential.
"However, they are well aware of the content of the programme, and they have been given the opportunity to respond."