LONDON (Reuters) - London brought in a new levy on the oldest and most polluting cars entering the city center from Monday, almost doubling how much motorists have to pay in the latest blow to diesel.

Drivers are already charged 11.50 pounds ($15) to enter the financial district and parts of west London under a congestion charge. But those driving petrol and diesel vehicles typically registered before 2006 will need to pay an additional 10 pounds.

Since the 2015 Volkswagen VOWG_p.DE emissions cheating scandal, a number of major cities including Madrid, Paris and Athens have announced plans particularly focused on cutting diesel emissions including bans, fines and restrictions.

The new charge could further encourage motorists to switch to greener models in one of Europe’s biggest cities as Mayor Sadiq Khan hopes the new levy to reduce toxicity, known as the T-Charge, will help save thousands of lives each year.

“The air is bad, but it’s also a killer,” he told Reuters. “There are children in London whose lungs are underdeveloped. There are adults who suffer a whole host of conditions caused by the poor quality air from asthma to dementia to suffering strokes.”

The tax will apply to up to 34,000 vehicles every month, according to Khan’s office, a small proportion of the 535,000 vehicles which come into the area. But it sets the tone for future policies including an ultra low emission zone due by the end of 2020.

Although the T-Charge will also affect older petrol cars, diesel has been particularly maligned over the last few years, with sales down 14 percent this year in Europe’s second-biggest car market as petrol demand continues to rise.

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“There’s a budget coming up and the government’s got to step up and announce the diesel scrappage scheme to help families and businesses,” said Khan, a politician from Britain’s main opposition Labour Party.

Britain’s Conservative government said this year that sales of new diesel and petrol cars would be banned from 2040 but has stopped short of an immediate program to incentivize drivers to trade in their old models.

Whether 40,000 Uber [UBER.UL] drivers, one in three of all private hire vehicles working in the British capital, continue to operate will also have a major impact on London’s streets in the years ahead.

The city’s transport regulator shocked the Silicon Valley taxi app last month by stripping it of its license. But the company can continue to operate until an appeals process is exhausted, which could take several years.

After discussions between Uber’s global Chief Executive Dara Khosrowshahi and Transport for London (TfL) Commissioner Mike Brown this month, Khan said further talks could take place.

“If it’s possible for the global CEO to continue discussions with the TfL commissioner of course that’s a sensible course of action,” he told Reuters.

“Whenever you can avoid litigation, you should avoid litigation but I appreciate Uber are appealing the TfL decision. We’ll have to wait and see how that pans out.”

(This version of the story adds how many vehicles will be affected)