Former senior Metropolitan police officers have reportedly criticised the force's leadership for its handling of alleged racism within the service amid the investigation of 20 officers and one civilian member of staff for alleged racist abuse.

John O'Connor, a retired Flying Squad commander, said it was not good enough for the deputy commissioner of the Met, Craig Mackey, to "wash his hands" of such incidents and wanted a more proactive approach to rooting out racism within the force.

A former detective chief inspector and founding member of the National Black Police Association, David Michael, said the force should use outside help to address police racism.

The controversy has engulfed the Met after the Guardian published a recording in which an officer could allegedly be heard racially abusing a detained 21-year-old. On Thursday, a number of other Met officers were referred or re-referred to the Independent Police Complaints Commission for investigation over alleged racist incidents, bringing the number of investigations to 10.

Speaking to the BBC, O'Connor said any criticism should be directed at the "leadership and management" of the force.

"We need to find out why this is happening. It's no good having the deputy commissioner almost washing his hands and saying: 'We won't put up with racism'.

"Well what are you doing about it? You need to do something," O'Connor said.

"It's a matter for the police to train and educate and select the right people so that these incidents don't occur," he said. "Why do you get officers who previously have had untarnished careers getting involved in these kinds of incidents? There are too many of these incidents for it to be brushed under the carpet and I think there needs to be more research."

Michael said: "The most important thing for the police service and all of those with governance responsibility for the police service, is to take the instances of police racism seriously, and to address it and use the help that's available from outside the police service."

O'Connor warned about the dangers of a witch-hunt against officers after it was revealed that fellow officers had reported a number of suspected racist incidents.

"Telling tales on each other is not good for morale," he said.

"You don't want a situation where a police officer says: 'I don't want to work with him because he grassed up a couple of other guys', and you don't want a situation where officers turn their backs on incidents which they think are suspicious and they're frightened to act because they feel there may be allegations made against them. You need to be very careful about how you handle these kinds of witch-hunts."

The Police Service of Northern Ireland revealed on Friday that it had suspended four officers after an internal inquiry into racist and sectarian text messages.

On Thursday, in response to the investigations, Mackey said: "There is no room for racism in the Met. Whilst any use of racist language is abhorrent, what is reassuring for me is that in the 10 cases that have been referred to the IPCC, six involve other officers who have stood up and raised concerns, showing that we are an organisation that will not stand for any racist behaviour."