Proposals to limit vehicle speeds to 60MPH on three new sections of Smart Motorway have been rejected by the Transport Secretary Patrick McLoughlin.

Mr McLoughlin said the speed limit on parts of the M1 and M3 set to be upgraded will remain at 70MPH.

The Highways Agency previously consulted on proposals to limit speeds to 60MPH between 7am and 7pm because of the potential effect of the new schemes on local air quality.

“Let me be absolutely clear," Mr McLoughlin said. "I want all motorways to run at 70MPH. While it sometimes makes sense to use variable limits to keep people moving, blanket reductions are not acceptable.”

He added that if any proposals continue to include varying speed limits, they must only apply when absolutely necessary.

Mr McLoughlin was speaking ahead of the start of works to convert parts of the M1 and M3 to Smart Motorway standard.

The sections of road being upgraded are the M1 junctions 28 to 31 in Derbyshire, M1 junctions 32 to 35a in South Yorkshire and on the M3 at junction 2 to 4a in Surrey.

These schemes are designed to boost capacity by a third and improve journey times by up to 10% on the M1 and 15% on the M3. The M1 schemes will begin operating in autumn 2015 and the M3 scheme will open in 2016.