LONDON (Reuters) - London Mayor Sadiq Khan declined to comment on Thursday on whether taxi app Uber [UBER.UL] will have its license renewed ahead of a decision due by the end of month, saying that giving a running commentary could prompt legal action afterwards.

An electronic billboard advertising Uber is seen in front of an office block in London, Britain, June 28, 2017. REUTERS/Toby Melville

Uber, which has faced protests from drivers of London’s traditional black cabs, had its license extended in May for four months as the city’s transport regulator considers several factors including a new fees system which could raise the costs paid by larger private-hire firms.

Several lawmakers wrote a letter this week calling on Uber’s license not to be renewed, accusing it of not being a “fit and proper operator” and criticizing its record on safety and working rights.

Asked about the upcoming decision during a question time session on Thursday, Mayor Khan said it would be wrong to comment ahead of the announcement.

“You would appreciate I’m sure how inappropriate it would be, bearing in mind that this is quasi-judicial role that is played, for me as the Mayor of London and Chair of (transport regulator) TfL to give a running commentary,” he said.

“If for no other reason, because they would then challenge that in the courts and say that the outcome of the application had been pre-judged.”

Uber has faced criticism in recent months over working conditions and later this month it will appeal against a decision by judges who ruled it should treat two of its drivers as workers and give them the minimum wage and holiday pay.

In recent weeks, the app has announced a series of measures in the UK capital, including the introduction of tipping and plans to stop using diesel cars by the end of 2019.

On Thursday, Uber said it was making further improvements for drivers by increasing some fares, allowing in-app messaging and committing to faster and easier administrative processes.

Uber’s General Manager in London Tom Elvidge said their cars remained a key part of life in the city.

“The app’s popularity speaks for itself with 3.5 million Londoners using it to get a reliable ride. More than 40,000 licensed private-hire drivers also rely on our app to make a living. We want to continue contributing to our city,” he said.