A notorious motorway speed camera which has increased the risk of accidents and caused huge tailbacks is to be scrapped.

The trap on the M4 has become a hazard during rush-hour as drivers brake sharply to avoid fines.

It has also triggered bunching, with motorists forced to stop and start along the 50mph stretch.

The Gatso’s axing is thought to be the first such move by highways officials on safety grounds.

Campaigner Paul Smith, of Safe Speed, said it was a landmark admission by authorities cameras can be counterproductive.

He said: "It’s a scandal. The side-effects are terrible and ensure that the cure is far worse than the disease."

The device was installed at Junction 41 near Port Talbot, West Glamorgan, in 2003 after a motorist died and three were seriously injured on the two-lane stretch in the three previous years.

The National Assembly for Wales admitted the camera caused congestion. Tory Assembly member Alun Cairns added: "The siting of it has always been nonsensical." The only time cameras have previously been decommissioned was in March when 30 failed to meet new rules ensuring they are clearly visible and installed only at sites of fatal or serious accidents.

But Philip Davies, of the Mid & South Wales Safety Camera Partnership, insisted the M4 camera had cut casualties. He said: "No one has been killed or seriously injured since it was installed."

Fears over the detrimental effects of cameras deepened last year when a probe was ordered over conflicting figures about their safety.

Another Government study found £5,000 flashing warning signs led to a 7mph fall in speeds and 34 per cent cut in accidents compared to 3.7mph and 14 per cent for £30,000 speed cameras.

The M4 trap will be replaced in the New Year by vehicle-activated signs that flash up warnings for drivers to slow down but do not fine those that trigger them by exceeding the limit.