Islington councillors are urging Sadiq Khan to make all buses operating from a Holloway depot zero emissions models by 2020.

City Hall released data collected by its "breath London" monitoring sensors in July, which identified the Holloway Bus Garage, in Pemberton Gardens, as a "hotspot" for high levels of air pollution.

The Mayor of London has pledged 27 per cent of buses running from the garage will be electric by October, and all vehicles must also now be Ultra Low Emission Zone (ULEZ) compliant.

But Islington's transport and environment chief Cllr Claudia Webbe and the three Junction ward councillors are calling for faster action after the "shocking" breath London data showed this location is on track to exceed its annual Nitrogen Dioxide limit.

When Boris Johnson was mayor, fewer than 25 per cent of buses at the garage were hybrid models.

Cllr Webbe said: "We're determined to do all that we can to improve air quality in Islington, as it is quite literally a matter of life and death for some people. The mayor has made some progress in moving to less polluting buses operating from the bus garage, but his own data makes it crystal clear that pollution remains shockingly high because of these dirty buses."

Green Party transport spokesperson Cllr Caroline Russell added: "The air pollution levels measured in Holloway Bus Garage are shocking. The mayor should urgently address these findings. Zero emissions buses should be rolled out as fast as possible and working practices in this very busy garage should be reviewed for their air pollution imact."

Cllr Janet Burgess (Lab, Junction) said: "Holloway Bus Garage sits in the middle of a densely populated residential area and it's our job as local councillors to do everything we can to make the operators and TfL minimise the impact it has on the lives of local people. Pollution levels remain far too high in the area around the bus garage and it's time that more was done, and quickly, to cut out these toxic emissions entirely."

Mr Khan has called "London's filthy air a public health crisis". His team has been approached for comment.