German Chancellor Angela Merkel announced plans on Monday to double to 1 billion euros ($1.19 billion) a fund aimed at cleaning up urban transport, in an effort to avert bans of diesel vehicles in some cities.

With an election due later this month, Merkel has come under fire for her close ties to Germany's powerful auto industry and for failing to crack down on vehicle pollution after Volkswagen admitted to cheating on US emissions tests.

On Monday, she met city mayors and regional leaders in a follow-up to a summit last month at which car bosses agreed to overhaul 5.3 million diesel cars to cut emissions, and set up a fund of 500 million euros to help cities limit pollution .

Merkel, who was on holiday when the summit took place, had faced criticism for not taking the lead in efforts to cut pollution in major cities in Germany, where courts are threatening to ban diesel cars if emissions do not fall.

As the election campaign heats up, Merkel has toughened her stance, lashing out at auto executives and urging them to do more to win back trust lost since the emissions scandal.

Merkel said on Monday that the fund would now be doubled to 1 billion euros, with the extra 500 million coming from the federal government, although she said the auto industry could also be asked to increase the 250 million it pledged last month.

‘We should do everything possible to avoid driving bans. We are all agreed we need an enormous effort,’ Merkel told a joint news conference with mayors of major cities. Another meeting with the auto industry will be held after the election, she said.

The prospect of diesel bans has unnerved drivers in Germany and prompted a slide in sales. Registrations of new diesel cars fell 13.8 percent in August to a share of 37.7 percent, the KBA motor vehicle authority said on Monday.

Merkel said local governments would be able to tap into the fund to pay for a range of projects, including better public transport, charging stations for electric cars, traffic control systems and more efficient delivery networks.

However, mayors for Berlin and Stuttgart warned that the authorities would have to move fast to cut emissions or risk courts imposing driving bans.

Related Story