Only half of police officers would report a colleague for beating up a suspect for attempting to escape arrest, a study into police ethics revealed.
Just 54% of officers said they would definitely report a colleague who "punched a suspect a couple of times as a punishment for fleeing and resisting", the Open University survey found.
Some 4.2% of officers - nearly one in 20 - said they would "definitely not" report such behaviour, while 6.5% said they would "maybe not" report it, 21.2% said they would "maybe" report it and 13.1% remained neutral.
After presenting officers with 11 such scenarios, the report concluded that officers were not willing to report colleagues' actions even when they were certain that behaviours were against the rules.
The Association of Chief Police Officers (ACPO) lead on professional ethics, Chief Constable Adrian Lee, said: "The research conducted by Louise Westmarland was fully supported by the ACPO Professional Ethics Portfolio and covered a range of scenarios along with that which has been reported, including for example, a question of an officer discovering a colleague stealing, where almost 100 per cent of officers said they would report them.
"It may be that the figures quoted in relation to the 'assault' question is more reflective of a lack of information rather than a reluctance to report. For example, were those who answered it considering whether this was an act of self-defence?
"While the research does point out the need to enhance the culture in this area, we need to examine closely how best to achieve this as a service.
"The vast majority of officers carry out their work with the highest integrity and professionalism and those who are found wanting are dealt in line with our regulations and in some cases, the criminal law.”
Monday's report comes on the same day that Met Commissioner, Sir Bernard Hogan-Howe, called for more training to raise policing standards.
The Met will pay for academics to conduct research into the best methods of policing and crime prevention.
Sir Hogan-Howe said: "Great professions like engineering and law have gained faculties in universities. Sadly, policing has not had that. That is a sad indictment," reports the Evening Standard.