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The Mercedes-Benz logo is pictured at the 2019 Frankfurt Motor Show (IAA) in Frankfurt, Germany, September 10, 2019. Reuters

Mercedes-Benz faces more than 300,000 claims at London's High Court from the owners of diesel vehicles that were allegedly equipped with "defeat devices" to cheat emissions tests.

The German carmaker is said to have misled customers about certain diesel vehicles' compliance with nitrogen oxide (NOx) emissions standards.

Mercedes-Benz denies that any defeat devices, which can change vehicles' emissions levels, were installed in its vehicles.

A spokesperson for the company said in a statement: "We believe that the claims are without merit and will vigorously defend ourselves against them."

The mass lawsuit follows the "dieselgate" scandal that engulfed Volkswagen after it admitted to cheating U.S. diesel engine tests, which has cost the carmaker more than 32 billion euros ($34 billion) in vehicle refits, fines and legal costs so far.

Nearly 300,000 claims have been issued against Mercedes-Benz in London with around 35,000 more in the pipeline, lawyers said at a preliminary hearing on Thursday.

Mercedes-Benz and the claimants have agreed the claims should be managed together.

Oliver Campbell, representing the claimants, said in court documents that certain Mercedes-Benz vehicles contained technology designed to lower NOx emissions, but that only worked properly at particular temperatures.

He said this meant the vehicles produced "far higher amounts of NOx than was permitted" and that Mercedes-Benz has no tenable defence to the lawsuit.

However, lawyers representing Mercedes-Benz denied its vehicles contained defeat devices, saying there was no reduction in the effectiveness of their emissions control systems.

Helen Davies said in written arguments that the lawsuit heavily relies on separate litigation in Britain brought against Volkswagen, which last year agreed to pay 193 million pounds ($235 million) to settle 91,000 claims without any admission of liability.

But, she added, there were "crucial differences" with the case against Mercedes-Benz, as its vehicles have not used any software that recognises when it is being tested for emissions.