Transport for London (TfL) has warned of significant traffic disruption in the capital as taxi drivers gear up to protest at rival cab service Uber.
The protest is the latest in a series across Europe as traditional cab services express anger over what they regard as a lack of regulation of Uber.
The protest will start in Trafalgar Square at 14:00 BST.
Cabbies are unhappy that Uber is using a mobile app to work out the cost of rides.
They argue this is tantamount to a taxi meter, which only black cabs are legally entitled to use in London.
The Metropolitan Police says conditions have been imposed on protesters after they failed to meet officers to discuss their plans.
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."
Cabbies claim that Uber is breaking the law by using an app as a taxi meter to determine the price of rides and is seeking a High Court ruling on the issue, which is expected to take several months.
"We have nothing against competition but we feel that Transport for London has failed Londoners by allowing Uber to operate outside the law," said Steve McNamara, of the Licensed Taxi Drivers' Association.
Up to 12,000 drivers are expected to take part in the protest.
Ch Supt Pippa Mills, of the Metropolitan Police, said organisers had failed to discuss the protest in advance, so the following conditions have been imposed on the demonstration:
- The protesters may assemble in Whitehall SW1, north and southbound carriageways and Parliament Street SW1, north and southbound carriageways
- The demonstration must not start before 14:00
- The demonstration must not end later than 15:00
- No-one will be allowed to join the demonstration when the area is deemed to be congested by the tactical commander of the event
Uber now serves more than 100 cities in 37 countries and has high-profile backers, including Google and Goldman Sachs.
It has 3,000 registered drivers in London.
The Institute of Directors has likened the protest to the machine-breakers of the 19th Century who tried and failed to stop the spread of the power loom.
"Black cabs have been a symbol of London for many decades, known across the world. But symbols, no matter how iconic, cannot be allowed to stand in the way of innovation," said director general Simon Walker.
"Uber and its rival apps are an example of the positive disruption new technology brings, offering consumers new choices about how to travel.
"The battle over taxi apps gets to the heart of what creative destruction means. As a nation, we have to decide whether we want to open ourselves up to more choice and competition, or protect existing industries at the expense of consumers," he added.
Uber was taking the protest in its stride and not missing the opportunity to advertise its services.
"Our technology allows us to identify areas where demand is high and we'll be helping Londoners to get around town quickly and efficiently," said Jo Bertram, UK and Ireland general manager.
It also announced that it would be opening up its car booking app to London's black cabs.
"There's room for black cabs and private hire cars to co-exist in London and we want to be part of a healthy, vibrant and diverse market," said Ms Bertram.
As well as London, traffic problems are expected in key European cities as traditional cabbies in Rome, Paris, Berlin and Milan join the protests.