File picture: Michael Dalder / Reuters.

London - Sales of new diesel cars have slumped by a fifth amid fears they will be hammered by tax hikes and charges, figures revealed yesterday.

Many motorists have become wary of investing in the latest models despite car-makers investing millions in cleaner engines.

Last month 81 489 newly registered diesel cars were sold, down 20 percent from 101 844 in May 2016. Sales of petrol cars edged up 0.4 percent to 96 518 while sales of alternatively fuelled vehicles, such as electric cars and hybrids, soared 46.7 percent to 8258.

But the Society of Motor Manufacturers and Traders, which published the data, refused to put the figures down to buyers shunning diesels despite the cars being hit by health fears and the VW emissions scandal.

The society blamed uncertainty caused by the general election for consumers delaying big purchases. It added a lull was expected because of the rush to snap up new cars in March before Vehicle Excise Duty went up on April 1.

But MPs and environmental campaigners said many motorists were clearly avoiding diesels amid health warnings and fears they face higher taxes and charges to drive into town centres. The market share of diesels has fallen from 50 percent over the last year to 43.7 percent while that of petrol cars has grown from 47.2 percent to 51.8 percent.

Charlie Elphicke, Tory candidate for Dover and Deal, has led calls for a fair diesel scrappage scheme and said the car sector was being hurt by the "demonisation of diesel drivers".

He added: "Threats by greedy councils of higher taxes on diesel drivers is bad for business. What’s more, it’s unfair as the latest diesels are as clean as petrol engine cars."

James Thornton, chief executive of legal activists Client-Earth, said: "People were encouraged to buy diesels and this helped fuel the air-quality crisis we have in the UK today.

"These figures could be a sign the penny is starting to drop, with people realising that many diesels produce pollution in towns and cities that harms human health."

Millions were encouraged to buy diesel cars by Tony Blair’s government because they are more fuel-efficient and emit less of the greenhouse gas carbon dioxide. There are now almost 12 million diesel cars on Britain’s roads.

But scientists and governments globally have since changed their tune as diesels emit more nitrogen oxides, which can harm health.

The VW diesel emissions scandal in 2015 has also led to accusations that carmakers have been cheating tests and playing down toxic emissions.

The Government is being forced by the EU to cut nitrogen oxides and beef up anti-pollution measures.

A draft plan includes encouraging councils to tackle diesel emissions. Ministers are also looking at changing the way diesel vehicles are taxed.