Motorists are being advised to avoid venturing into central London on Wednesday amid plans by taxi drivers to block roads in a row over regulation.
Commuters, visitors and workers in the capital are likely to experience travel chaos as thousands of black cab and licensed taxi drivers cause gridlock during their protest.
The dispute centres on a new phone app which means consumers can book and track taxis.
According to industry unions, unlicensed drivers can be contacted through the app, with no checks on whether or not they are legitimate.
Drivers have decided to take direct action despite the fact that legal action against Transport for London (TfL) is already under way.
Steve Garelick, of the GMB union's professional drivers branch, claims that the app - and the predicted rise in unregulated taxi drivers - is a "hammer blow" to the legitimate taxi and private hire industry.
But Garrett Emmerson, TfL chief operating officer for surface transport, said the protest will cause "pointless disruption".
He urges commuters to walk or take the Tube, and warns cyclists to take extra care on their journeys.
Copyright Press Association 2014