Motorists could be charged to drive to the shops under plans backed by Sadiq Khan to discourage “needless” car use.
The Mayor has given his support to a call for London to introduce road-user charging, which would set a levy based on the distance and time of day travelled.
Supporters say that charging drivers to make journeys that could be walked, cycled or made by public transport would end decades of “the car being king”.
The idea has been proposed by Camden council transport chief Adam Harrison, who is overseeing the transformation of Tottenham Court Road and Gower Street into two-way streets that prioritise pedestrians and public transport.
In an article for the Fabian Society, Mr Harrison compared driving half a mile to the shops to “the cheeky cigarette you know you shouldn’t be having”.
He said: “The truth is that reclaiming London’s streets for public use over private domination will make London a better city.
"A nuanced charging system could be variable by time of day, the type of journey being made, the vehicle used and the alternatives available.
“The journey in a clean vehicle with no reasonable walking, cycling or public transport alternatives could be charged at a low rate, or not at all, while the needless drive down to the shops could be charged more.”
Mr Khan said he wanted to avoid a “war on motorised road users” and road-user charging would have to replace vehicle excise duty, which costs London motorists £500m a year.
Any new system would also incorporate the congestion charge and ultra low emission zone (Ulez) into a single levy.
Mr Khan has asked Transport for London to investigate the technology available to introduce road-user charging, but said it would not be introduced “in the short term”.
He told the Standard: “We are going to continue to invest in new technologies around the ultra low emission zone but look into what is available in relation to technology around road-user pricing.
"What you can’t afford to do is to have London motorists being penalised twice — paying vehicle excise duty and road-user pricing.
“Once we are confident in relation to road-user pricing, if councils like Camden want to test it or pilot it, of course I would be happy to work with them.” London is due to hold its biggest-ever Car-Free Day this Sunday when more than 340 residential roads across 24 boroughs will be turned into “play streets”.
The centrepiece of the event, backed with £1m from City Hall, will be the closure of Tower Bridge and Bank junction, with festivals at both locations.