Critics have also claimed that the introduction of cameras aimed at enforcing the 70mph limit, is not about road safety but about generating income through fines.
The new devices are grey, rather than the highly visible yellow cameras often used around roadworks, raising fears that motorists may be caught off guard.
Studies have shown that as many as 95 per cent of drivers admit to breaking the limit on motorways.
The introduction of cameras on one stretch of the M25 in Kent alone has led to almost 700 drivers receiving fines in little over two months.
Some cameras were installed on a northern section of London’s orbital motorway before Christmas, and more will be deployed on busy stretches of some of the most important motorways including M1, M3, M6 and M60 over the next few years.
In 2013, Patrick McLoughlin abandoned plans to introduce a new 80mph speed limit on Britain's motorways amid fears the change would alienate women voters.
A Highways Agency spokesperson said: “Variable speed limits on smart motorways are primarily there to smooth traffic flow, reduce congestion and make journeys more reliable.
“Hundreds of thousands of motorists use this stretch of the M25 every day. The vast majority are sticking to the speed limits and are experiencing better journeys as a result of smart motorways.
“There are clear signs where cameras are in place and the new cameras are more visible than the previous versions.”