The “all lane running” plan is an extension of existing schemes where the the hard shoulder is used at peak times or to deal with congestion.

The Committee said that the permanent loss of the hard shoulder in all lane running schemes was a “radical change and an unacceptable price to pay for such improvements.”

Committee chair Louise Ellman said: “The permanent removal of the hard shoulder is a dramatic change.

“All kinds of drivers, including the emergency services, are genuinely concerned about the risk this presents.

“It is undeniable that we need to find ways of dealing with traffic growth on the strategic network.

“But All Lane Running does not appear to us to be the safe, incremental change the Department wants us to think it is.

“While ‘smart motorways’ have existed for years, this is fundamentally different.

“Government needs to demonstrate that All Lane Running schemes do not make the road any less safe that the traditional motorway with a hard shoulder.

“The Government has a model which has worked. The scheme on the M42 has a track record of safety and performance but subsequent versions have gradually lowered the standard specification.

“The most recent incarnations of All Lane Running have less provision for safety measures than original pilot schemes.

“Government needs to demonstrate considerable improvement in this area, including more emergency refuge areas, driver education and enforcement, before the Committee will endorse the extension of a scheme which risks putting motorists in harm’s way.”

Plans are in place to permanently convert the hard shoulder into a running lane on around 300 miles of motorway.

Highways England has a programme of 30 all lane running schemes worth £6bn over the next nine years.

Industry experts disagree with the MPs.

Simon Benfield, Team Director: Bridges South, at consultant Ramboll said: “The hard shoulder on motorways represents a perception of safety that is greater than the reality.

“All that separates the hard shoulder from 70mph traffic is a white line. Despite projecting a sense of safety, over 1,500 people are killed or injured every year on the hard shoulder.

“Research indicates that in the large majority of cases, where there is no hard shoulder available, drivers are able to push on and reach the nearest lay-by as has been seen on the trunk road network for many years.

“The psychological impact of having a hard shoulder available is that drivers are more likely to use it when they actually don’t need to.

“In addition to this, there has been an overall reduction in collisions where Smart Motorways operate with hard shoulder running in effect, either temporarily or permanently due to the effects of greater control.

“By adopting Smart Motorways over traditional widening it is possible to provide improvements in many more areas around the network thus providing a positive improvement for many more people.

“When compared to the physical widening of motorways, Smart Motorways are 20-40% more cost effective and therefore applying a level-headed approach to the opening of hard shoulders is a sensible way forward.”