Environmental pressure group Client Earth has called on the delay to the introduction of clean air zones (CAZs) to be kept as “short as possible”.

Earlier this month the Government announced that the introduction of CAZs is to be delayed until after it overcomes the coronavirus pandemic.

Rebecca Pow, a junior minister at the department for Food, Environment and Rural Affairs (Defra), says the move will provide “certainty” to the commercial fleet industry.

A spokesman for Client Earth said: “The Government has committed to keeping any delay to putting CAZs in place “as short as possible”.

“Given the harm to people’s health caused by air pollution, particularly to those most vulnerable, we think this is essential.

“Many people have noticed cleaner air in towns and cities during the lockdown, but this is an unintended consequence of the unprecedented decisions that the Government has made to protect the population from Covid-19 and any impacts on air quality prompted by these is likely to be short lived.”

CAZs, which aim to deter the most polluting vehicles from entering the most polluted parts of towns and cities, have been identified by the UK government as the quickest way to improve air quality.

A report from the London Assembly has shown that London’s ultra-low emission zone (ULEZ) has reduced nitrogen dioxide pollution by up to 37% in the three month period before the lockdown, compared to a scenario where no ULEZ was in place.

CAZs were due to be implemented in Birmingham, Leeds and Bath this year, but it has been suggested that these will be delayed until at least January 2021.

Additionally, the congestion charge, low emission zone and ultra low emission zone in London have all been suspended until further notice and a tightening of standards for the low emission zones, due in October, has been pushed back.

CAZs are due to be introduced in other towns and cities from 2021, including in Bristol, Sheffield, Newcastle, Manchester and Portsmouth. Recent announcements suggest that these timetables may also be under threat.

An already-delayed consultation on Greater Manchester’s proposals planned for this summer has now been indefinitely postponed.