Hammersmith & Fulham council will fine motorists who fail to switch off their engines when stationary, causing unnecessary air pollution.
The new powers form part of an experimental traffic order which comes into effect from 1 November and will last 18 months. They will then be reviewed, with the potential to be made permanent.
The change is part of the councilâ€™s drive to tackle poor air quality in areas of the borough where traffic pollution is highest, it has said.
Under the new powers, traffic wardens will be able to issue a Â£40 penalty charge notice to motorists who have stopped with their engine idling in parking and loading bays, taxi ranks, or any roads where waiting is restricted. The fine will increase to Â£80 if not paid within 14 days.
Cllr Wesley Harcourt, H&F Cabinet Member for the Environment, said: â€œThis is a major advancement in stopping motorists needlessly polluting our streets and helping us become the greenest borough in Britain.
â€œPreviously, we could ask motorists to switch off, or face a Â£20 fine, which was not enough of a deterrent. So now weâ€™re taking a harder line to help reduce the harm from air pollution to our residents.
â€œWeâ€™re particularly keen to reduce the effects of nitrogen dioxide on children in the borough, who are often at higher risk, due to being closer to the height of exhaust fumes.â€
The council will review the scheme and if considered successful it could be made permanent.
Civil enforcement officers have previously worked with other organisations on â€˜anti-idling action daysâ€™, where council staff and local volunteers spoke to idling drivers asking them to switch off their engines.
In 2015 the council formed the resident-led Air Quality Commission to investigate air pollution in the borough, causes and dangers, and explore possible solutions.