"With more than 20 years as a traffic inspector and chief inspector, I always thought that, when decisions were made to prosecute motorists, the police had to prove the offence beyond all reasonable doubt - and that they also had to use a certain amount of discretion and commonsense.
"Now I believe those basic principles are being ignored in pursuit of revenue."

He added: "I am not in favour of speeding, but I am in favour of cameras being sited properly based on proper accident statistics and for using mobile cameras instead of fixed ones where possible."

He said the way police accident figures were calculated had changed in recent years, which must mean the way decisions are made about where to site fixed speed cameras must be "skewed." He believes more mobile speed guns should be used because some fixed cameras may not be useful as road-safety tools.Mr Longsden, who was a police officer for nearly 35 years and a traffic officer for more than 20 years before his retirement in 1995, spoke out after speeding tickets were issued to more than 20 drivers caught driving at 10 mph over the limit near Oldham.The camera on the A663 Broadway, near the junction with Eustace Street, had apparently been reset from 40 mph to 30 mph before roadworks began but the drivers say the change was not properly sign-posted. More than 20 drivers who were issued with fixed penalty fines after being caught driving at 40 mph are joining together to fight their prosecutions. They say they are determined to take their battle to court instead of paying immediate fixed penalty fines.

Mr Longsden said: "This particular camera on Broadway, for example, may have been needed when it was put there many years ago, but it is very close to a pedestrian crossing and might not even be necessary now."

A spokesman for DriveSafe, responsible for the region's 185 speed camera sites, said they are reviewed every year by the Department for Transport.

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