Transport for London has been asked to work up the idea, which is still little more than a concept.
The Mayor hopes to follow the lead of Paris, Oslo, Madrid and Boston in developing road transport tunnels as a radical solution to growing congestion problems in the Capital.
The proposed route would have up to 10 portals. A dual carriageway tunnel would circle north London from Camden to Highbury, then head south east to Shoreditch and Wapping whether the tunnel would run under the Thames to Elephant and Castle, and then to Battersea.
It would then cross under the Thames again at Chelsea, and sweep through Earls Court to St John’s Wood, before returning to Camden.
TfL forecasts a 60% surge in congestion in the central zone by 2031 if nothing is done, while outer areas would suffer increases in congestion of 15 to 25%.
Some of the costs for the ambitious plan would be met by freeing up development sites worth billions of pounds that are presently strangled by congested transport routes.
Isabel Dedring, Deputy Mayor for Transport, told the Evening Standard: “We are at the very early stage in exploring the potential.
“This is not about creating a motorway through the centre of London. It’s about freeing up capacity on the city surface, improving air quality, and reclaiming space for public parks, pedestrians and cyclists.”