A politician has waded in on a debate around plans to impose a 20mph speed limit in central London, saying there is “no guarantee” it will reduce harm.

On Tuesday, the Mayor of London, Sadiq Khan announced a ‘Vision Zero’ action plan to reduce the number of serious injuries and deaths on all Transport for London (TfL) networks.

Central to his plans were proposals to make 20mph the new speed limit on all TfL roads within the Congestion Charging Zone – which covers central London – by 2020.

Many London politicians raised concerns about the plans and expressed opinions that these limits should also be applied to outer London.

London Assembly member for Havering and Redbridge, Keith Prince, says however that introducing this speed limit could increase congestion and worsen London’s air pollution through more idling.

He added: “The safety of Londoners should always be the Mayor’s absolute priority, but safety measures need to be implemented in a balanced and proportionate way.

“There is no guarantee that this move will reduce harm – evidence from other parts of the country shows that reducing speed limits to 20mph has actually increased the number of deaths and serious injuries.

“It is incumbent on Sadiq Khan to demonstrate that this policy will improve Londoners’ safety and not have any damaging side effects.”

Mr Prince also appeared on LBC to discuss the issue yesterday – tweeting about it afterwards he said that Mr Khan should spend money on policing if he wants to stop deaths.

Other London assembly members who raised concerns about the plans included Green party assembly member Caroline Russell who said that Mr Khan needs to be “bolder” with his plans and commit to a least trialling 20mph speed limits in outer London.

The chairman of the London Assembly transport committee Caroline Pidgeon also thinks the mayor needs to impose these limits to outer Londoner.

Referring back to the transport committee’s ‘Hostile Streets’ report Ms Pidgeon said: “Although this announcement is a start, the Mayor and TfL need to be more ambitious outside the Congestion Zone, where there is huge untapped potential for more walking and cycling.”

By 2022 the mayor wants to reduce the number of people killed or seriously injured on London’s roads by 65 per cent, with no-one being killed by a bus by 2030.