Thousands of taxi drivers brought central London to a standstill today during a “go-slow” protest against a mobile phone app that is undercutting their business.

A giant snake of black cabs choked Whitehall, the Mall, Victoria Embankment, Victoria Street, Piccadilly, Regent Street and countless other roads.

The cab drivers claimed to be acting in defence of their livelihoods, but for the organisers of a protest estimated to have cost the capital more than £100 million, it was also the opening salvo in a political war against Boris Johnson, the London mayor.

The Metropolitan police imposed an hour-long limit on the stoppage and set geographical boundaries. A spokesman said no arrests were made even though neither condition appeared to have been met.

At the heart of the dispute was a preliminary ruling by the mayor’s transport team that the Uber mobile phone app, which uses GPS tracking to measure time and distance to calculate fares, was different from a “taximeter”, which can only be carried by black cabs.

Uber claims that its passengers pay up to 50 per cent less than black taxi fares. Payments are made through a Dutch company, leading to claims that Uber is trying to avoid UK taxes, but the company insists that it pays everything it owes to the taxman.

Key roads were blocked by two lanes of black cabs in both directions as drivers congregated around Trafalgar Square. Bemused tourists looked on as taxi drivers stood in groups chatting next to their stationary vehicles.

Hundreds of would-be cabbies taking the “Knowledge” sounded the horns of their scooters as organisers from the RMT and GMB unions led chants of “Boris, Boris, Boris, out, out, out”.

Lewis Norton, of the RMT taxi drivers’ branch, said: “This is an ideological attack on public transport to give more power to the private sector and big business from America.”

Mr Johnson said: “Black cab drivers are the face of London. There must, however, be a place for new technology to work in harmony with the black cab, and we shouldn’t unnecessarily restrict new ideas that are of genuine benefit to Londoners.”

The protest organisers believe that Mr Johnson is failing to implement laws designed to safeguard their trade. They also accused him of calling in the police to disrupt their lawful protest.

Steve McNamara, general secretary of the Licensed Taxi Drivers Association, clutching a public order notice served by officers before the protest had even begun, claimed that Mr Johnson was unfairly siding with Uber’s “pick-up service” and its backers, including Google and Goldman Sachs.

Jo Bertram, of Uber London, said: “Unsurprisingly, the LTDA, which is stuck in the dark ages, is intent on holding London to ransom and causing significant economic impact to Londoners today, estimated to be £125 million.”