AMBITIOUS targets for reducing carbon dioxide would be blown off course if motorway speed limits were increased from 70mph to 80mph, a leading expert on transport emissions has claimed.

Research by Jillian Anable, senior lecturer at the Centre for Transport Research at Aberdeen University, found the speed increase would lead to an extra 1.3 million tonnes of CO2 across the UK every year.

Enforcing the 70mph limit more strictly, however, would lead to a drop of 1.3 million tonnes of CO2, she found.

The figures were published after Westminster Transport Secretary Philip Hammond launched a consultation on Thursday on a 10mph increase on motorway speed limits, claiming it would benefit the economy.

However, Ms Anable, a leading authority on CO2 emissions in transport, who has researched the subject for the Scottish Government, said this would threaten targets to reduce carbon emissions by 80%, based on 1990 levels, by 2050.

Of the 500 million tonnes of carbon produced across the UK economy, transport accounts for 70 million tonnes and is one of the few sectors where emissions are expected to grow.

“This flies in the face of the targets for reductions in carbon emissions. Every bit of analysis that’s been done says we have to throw everything we have at the problem, particularly in transport, because with rail, aviation, shipping and HGVs there is very little scope to reduce emissions, you have to rely on cars,” Ms Anable said.

“There are not many levers to pull and the one we have we’re thinking of pushing it in the wrong direction.”

A Scottish Government spokesman said it would “consider the implications for Scotland” over speed limits, which are due to be devolved next year as part of the Scotland Bill.