Certain cars could be entirely banned from London's streets in an effort to combat the city's "toxic" air, mayor Sadiq Khan has hinted.
The UK capital's mayor, who has already announced plans for drivers of some of the oldest and most polluting cars to pay a £10 "toxicity charge" to drive in central London from October, suggested he could go further.
Asked if that meant he was considering the option of banning some drivers from entering the city on certain days, Mr Khan said "nothing's off the table".
He also said there was an "issue" with wood-burning stoves which have become popular in recent years.
Air pollution is linked to 9,000 early deaths a year in London, one of many places hit by the UK's air quality crisis, which has prompted the European Commission to issue a "final warning" to the Government for repeated breaches of legal limits.
On ITV's Peston on Sunday, Mr Khan was asked whether he was considering going further than the T-charge plan and could ban driving on certain days.
Mr Khan said: "Well, nothing's off the table but I want to address the issue of poor quality air 365 days a year, not only on those days where the air is dangerous."
Pressed on whether, if he was alerted that air was reaching dangerous levels of pollution he would announce a ban on certain cars driving that day, he again state that "nothing's off the table".
Asked about the impact of wood-burning stoves, Mr Khan said: "Well there's an issue, I mean I issued the first ever very high air pollution alert a few weeks ago and the experts say one of the reasons was during that particular weekend lots of those stoves were being used.
"We've got to work with manufacturers to make sure the right sorts of stuff are being burnt in these stoves but you know one thing by itself won't be enough, that's why the Government has got to help me in cities around the country to address this massive issue."
Mr Khan suggested the Government should introduce a scrappage scheme for diesel vehicles and a clean air act to combat pollution.
"I'm saying to the Government, you need to introduce a national diesel scrappage fund to help people, especially the poorest families, businessmen and women with vans to move from diesel to cleaner forms of transport. Some people need to drive a van, need to drive a minibus, need to drive a car, they've got to help me.
"But also, we need a clean air act, fit for purpose for the 21st century. Half of emissions come from road, the other half come from construction, housing and the river. The Government's got to step up to the plate."