Motoring campaigners have called for a rethink of police training after an investigation revealed major differences in the way forces deal with officers caught speeding.

The RAC Foundation said the detailed study showed some forces were over-using exemption powers and suggested some police officers believed they had "carte blanche" to break the speed limit regardless of whether they were on a 999 call.

In all, forces admitted officers had triggered speed cameras a staggering 45,741 times.

In the vast majority of cases, officers were exempted from fixed penalty fines and prosecution because they were speeding on a 999 call or on other operational duties.

Only 934, or two per cent of the total, were given a #60 penalty ticket, taken to court or still had cases pending.

The league table, compiled by the Press Association, shows startling differences in the rate at which speeding offences are committed by different forces each year.

Officers from Essex Police - considered the home county of the "boy racer" - topped the table with 5,269 in just six months, a rate of 3.26 per officer per year. bSecond highest was Bedfordshire with 2,519 in a year, or a rate of 2.04 for each officer.

In the Midlands, West Mercia recorded a rate of 0.54 speeding incidents per officer; West Midlands 0.23 and Staffordshire 0.91.

Warwickshire was one of nine forces which refused to disclose information.

The survey data, obtained under the Freedom of Information Act, showed huge variations in the number of speeding cases in neighbouring forces, and in how senior officers decided to deal with them.

For example, Essex had 5,269 in just six months while neighbouring Suffolk reported just 40 in a year.

The RAC Foundation's head of traffic and road safety Kevin Delaney, who was a policeman for 30 years, said: "The exemption rules are pretty widely misunderstood by rank-and-file officers as giving them a carte blanche exemption from the speed limit when driving a police vehicle.

"That is clearly wrong and suggests something is wrong with police driver training. Forces with the lowest number of camera triggers and higher proportions of officers refused an exemption have clearly taken a stand on this."

He added: "It is difficult to explain the huge difference between the Met and Greater Manchester Police, which are both large urban forces with presumably broadly similar numbers of cameras.

"It seems the Met is working from a presumption that every cop who triggers a speed camera must have a good reason to do so. That presumption is the wrong way around."

Forces could save the taxpayer a huge amount in maintenance and fuel costs by driving more slowly, he said.

An Essex police spokes-woman said it was "over-simplifying the situation" to make direct comparisons as there were other factors that needed to be taken into consideration.

She added: "Legislation gives an exemption to drivers of emergency vehicles in certain circumstances and every activation is assessed to ensure the driver has complied fully with the legislation.

"If any officer is found to not to comply positive action will be taken."

Pc Norman Brennan, head of Protect the Protectors, said: "Police officers are exempt from speed limits if complying with them would slow their response time when attending an emergency with a view to saving lives or arresting someone committing a crime.

"However, if whilst responding to an emergency call an accident occurs police officers are subject to road traffic regulations and prosecution like any other motorist.

"Police are trained to a high standard, if called to exceed the speed limits they are able to do so safely." The accident rate for police 999 calls is lower then for most drivers.