The London Taxi Company, now renamed the London Electric Vehicle Company (LEVC), has lost its latest attempt to trademark the shape of the capital's black cabs.
The Court of Appeal upheld a decision made by the High Court last year that the shape lacked "distinctive character", and was not a "valid registered trademark".
London Taxi Company had claimed that Frazer-Nash and Ecotive deliberately created a cab to resemble its vehicles.
The court today upheld the previous judgement, rejecting the passing off claim, which Frazer-Nash and Ecotive said will allow them to start production of its new Metrocab.
Law firm Berwin Leighton Paisner advised the two companies, with partner Rupert Ticehurst saying: "I am delighted that we have succeeded in this disruptive litigation so that the taxi can go into production. The Metrocab will bring quiet and green taxis to London."
The London Taxi Company has though, indicated it could yet take the case to the Supreme Court.
In a statement, it said: "LEVC has noted the decision of the court and will be making no further comment while we review the judgment and consider our options."
In July, the London Taxi Company announced its change in direction - and name change - with a £325m investment from Chinese parent firm Geely, along with the unveiling of the first look at London's new electric black cab.
The test fleet drivers are London cabbies and will help to collect information such as the emissions savings being made, as well as the performance of the capital's charge point infrastructure. That will all be compiled before the cars are delivered to customers and made available to fare paying passengers later in the year.