Taxi drivers will bring central London to a standstill on Wednesday in a bitter dispute over claims that the industry is being deregulated, raising safety concerns.
Thousands of black cabs and licensed taxi drivers will block roads in the capital, causing travel chaos for commuters, visitors and workers.
The row has flared over the introduction of a phone app allowing customers to book and track vehicles. Unions and groups representing taxi drivers are warning that the move is leading to unlicensed drivers being contacted via the new technology, with no checks on whether they are legitimate.
Legal action is being taken against Transport for London (TfL) but drivers are taking direct action, starting with Wednesday's protest.
Garrett Emmerson, Transport for London's chief operating officer for surface transport, said: "A number of taxi drivers are set to cause pointless disruption for Londoners over a legal issue that is down to the courts to decide upon.
"TfL will work with the Metropolitan Police to do all we can to keep central London moving. However, given the scale of the likely disruption, we would advise drivers to avoid the area if at all possible. There are lots of other ways to get around, including the Tube or walking, and we're asking cyclists to take extra care given the large number of vehicles expected to be involved."
"There must be a obligation to keep trade to the groups who are paying for legitimate licences in their district.
"We have campaigned on uninsured and unlicensed operators and drivers for many years and we cannot ignore the facts that at present many individuals are slipping through the net."
Mick Cash, acting general secretary of the Rail, Maritime and Transport union, said: "The attack on the professional licensed taxi trade by a combination of mayor Boris Johnson and wealthy global corporations seeking to maximise profits is nothing short of a scandal.
"We would urge the people of London to back their cabbies 100%. There will be serious disruption on Wednesday but that will be nothing compared to the disruption and dangers of allowing our licensed taxis to be driven from our streets through a combination of ignorance and greed."
London cab driver mishears drunk passenger and takes him to Belgium
London taxis voted the best in the world