A motorway speed camera blamed for causing accidents generates up to half a million pounds a year in fines.

Crashes have risen by almost a quarter and casualties have almost doubled since the camera was installed on a busy stretch of the M11 in Essex, in 2000.

Now, details revealed under Freedom of Information legislation, show that the device results in up to 9,000 speeding tickets a year, enough to raise around £500,000.

Campaigners have accused the authorities of refusing to remove the camera, despite it being linked to accidents, because of the revenue it brings them.

Paul Pearson, who runs motoring website said: "No wonder they haven’t removed the camera that is causing these accidents. It is just raising too much money and they clearly want to keep it there."

Essex Police, which runs the camera together with Essex Council and the Highways Agency, had initially refused a Freedom of Information request by Mr Pearson for details about the speeding tickets issued by the machine.

But after a ruling by the Information Commissioner, the police have been forced to disclose that in 2003 alone the M11 camera was responsible for 9,639 fines and a further 8,451 in 2004. The following year 9,047 motorists were caught by the camera and in 2006 a total of 7,801 were sent fines. In 2007, the number fell to 3,305. There are no complete figures for 2008, but in the year up to May 2009, the number of fines had risen to 6,445.

Mr Pearson has highlighted the danger he claims the camera poses, after he put in an earlier Freedom of Information request, having witnessed an accident on the road.

The data showed that in the five years before the camera was installed, there were 13 accidents and 14 casualties in the area. In the following five years, the number of accidents rose to 16 and casualties to 24.

At the spot, between Junctions 5 and 4 on the soutbound carriageway, the motorway’s three lanes narrow to two and the speed limit drops from 70mph to 50.

The Highways Agency said that the accident data did not show a pattern of accidents which would be consistent with the camera itself being a factor.

Police have blamed motorists who slow down ahead of the camera and then speed up once they are clear of it.

A spokesman for Essex police denied the camera was causing crashes. He said it was not being kept for revenue reasons and that there were no plans to remove it.

He said that police recently added an extra ’speed indicator’ sign that displayed approaching motorists’ speeds before they reached the camera, in addition to camera warning signs and 50mph signs.

"Cameras do not cause collisions, poor driving does," said the spokesman.