Lowering limits would reduce the amounts of noxious gases emitted by vehicles at high speed and reduce polluting traffic jams.
Speed limits could be lowered to 60 miles per hour (96km/h) on sections of several British motorways in moves to meet European Union rules on fighting dangerous levels of air pollution.
The move marks a change of policy just two years after the British Government was advocating an increase from 70mph to 80mph (112km/h-128km/h) on major routes to shorten journeys and boost the economy.
A 60mph speed limit is set to be introduced on a congested 50km stretch of the M1 in Derbyshire and South Yorkshire to cut pollution levels and could also be brought in on other sections of road across the country if air quality is at risk.
The initiative was welcomed this week by environmental campaigners, while motoring groups warned of the danger of confusing drivers forced to switch between speeds on different stretches of motorway.
The proposed reduction to 60mph on the M1, which has gone out to consultation, was forced by a Highways Agency scheme to turn parts of the hard shoulder into an extra lane. It has been warned that the additional traffic that would be generated would push pollution above levels allowed under new EU restrictions.
Lowering limits would reduce amounts of noxious gases emitted by vehicles at high speed and reduce polluting traffic jams, the Highways Agency believes.
Both the agency and the Department of Transport confirmed the 60mph experiment could be rolled out to other stretches of motorway in England and Wales where hard shoulders are brought into use.
Similar "managed motorway" schemes, where speed limits are varied and hard shoulders brought into use, are planned on parts of the M6, the M8 and the M25.
In 2011 former Transport Secretary Philip Hammond provoked controversy when he signalled his support for a rise to 80mph.
However, his successor, Patrick McLoughlin, has shelved the idea following warnings that an increase would lead to fatal accidents.
The Highways Agency said the planned restriction would apply between 7am and 7pm every day of the week.
The Highways Agency's argument that the proposed reduction would reduce traffic congestion is based on the "red light domino effect", the idea that as soon as the car ahead brakes and the red light comes on, each of the cars behind will, in turn, put their brakes on. The faster the speed, the greater the need to break and the chance of slowing down.
The AA president Edmund King said: "It's the only way to reduce emissions until the technology kicks in and makes engines cleaner, so it's something we have to live with. You can't really be against it, but many drivers will be frustrated and bemused. Earlier this year there was talk of an 80mph speed limit and now it's gone down to 60mph."
The Roads Minister Robert Goodwill said: "Any speed restrictions to improve air quality would be temporary, only ever considered as part of road improvement work and would not be appropriate for the vast majority of projects started in this Parliament."
But Mary Creagh, the shadow transport secretary, said: "These proposals could confuse motorists who have to adapt to variable speed limits on managed motorways."
Tailbacks on motorways form for numerous reasons - from drivers slowing down to "rubber neck" at an accident to something as simple as one car braking heavily.
That forces the car behind to brake heavily a couple of seconds later. This concertina effect can lead, a few miles down the road, to the bane of the motorway journey - stop-start traffic.
To avoid this, the Highways Agency has already introduced variable speed limits, slowing traffic to 40 or 50mph in order to allow the congestion ahead to clear, and to prevent drivers having to slow rapidly from 70mph. By the time they hit the slow-moving traffic, they should be travelling at the same speed.Independent