A survey by The Independent has found that there are 800 officers in England and Wales, almost all of superintendent, inspector and sergeant ranks, working on complaints and anti-corruption inquires.
Their salaries cost an estimated pounds 30m a year - equivalent to the pay of 1,300 police constables.
The study has also revealed that a record number of police forces are being used by the Police Complaints Authority (PCA) to carry out investigations into other forces.
There are 19 ongoing PCA inquiries into serious cases that include allegations of intimidation, deaths in custody, and sexual harassment.
The Home Office and chief constables are concerned about the growing numbers of officers and resources being diverted to examine the conduct of the police rather than concentrate on fighting crime in the community. A review is being carried out to bring about savings and improvements.
One idea being examined, which has the backing of police chiefs, is a national network of independent ombudsmen attached to each force.
Until now there has been no national figure available for police personnel employed in investigating fellow officers.
The Independent contacted all 43 forces in England and Wales and obtained details of the number of people working in the complaints and discipline department and in specialist anti-corruption units.
In the handful of cases where forces refused to give details the numbers have been estimated by comparing them with similar-sized forces. Figures have also been obtained for the number of officers working on behalf of the PCA to investigate outside police forces.
The Metropolitan Police have by far the largest number with 302 officers. Of these 214 are members of the pro-active unit, CIB3, which is spearheading the Met's largest anti-corruption drive for decades. So far, nearly 60 officers have been suspended or charged as a result.
Merseyside Police have a 20-strong professional standards department, a confidential telephone hotline for officers, and a pro-active squad. West Midlands Police have a similar set-up but employ 23 officers and 15 civilians in their department, and in a separate anti-corruption unit.
Several forces use specialist units for serious allegations of corruption within their own force. South Yorkshire have a team of eight investigating allegations of fraud involving the Government's handgun compensation scheme.
But even smaller forces invest significant resources. For example, Norfolk's complaints and disciplinary department is staffed by a superintendent, two chief inspectors, four inspectors, two sergeants and three civilians.
The forces that refused to give any information, arguing that it was confidential, were Greater Manchester, Hertfordshire, South Yorkshire, Humberside, and West Yorkshire.
In addition, the survey found there are about 85 officers deployed on PCA-supervised investigations outside their own force area. The largest case involves 20 staff from Essex Police who are investigating the death of Roger Sylvester, a black man who died in January after being restrained by eight police officers in north London.
A PCA spokesman said: "The number of outside forces used has increased. During 1998-99 at least 25 outside forces will have conducted PCA supervised investigations compared to 14 in 1995-96."
The current total of 19 live investigations is believed to be a record.
Next month new measures come into force to make it easier for chief constables to sack incompetent and corrupt officers.
George Hedges, Chief Constable of Durham and spokesman on disciplinary issues for the Association of Chief Police Officers, stressed that only 0.5 per cent of the complaints made to the PCA were allegations of corruption.
"At the moment there's no alternative but to investigate all complaints however minor.
"There's a massive waste of resources going to look at complaints.
"One idea is to have an independent legal person attached to each force to deal with the less serious cases. This is something we are looking at," he said.
Chief Superintendent Peter Gammon, president of the Police Superintendents' Association, added: "There's no question that disciplinary issues are an enormous expense costing millions of pounds, but you need a system that the public has confidence in and that demonstrates that wrongdoers will not be tolerated."Reuse content