Demand for new diesel cars plummeted by a fifth last month amid rising concerns over air pollution.

Approximately 81,500 new diesel cars were registered in the UK in May, down 20% on the same month last year, according to the Society of Motor Manufacturers and Traders. This represented a fall in market share from 50% to 43.7%.

The fall comes amid a flurry of negative publicity around the impact of diesel-fuelled vehicles on the environment and people’s health.

Air pollution has been linked to an estimated 40,000 early deaths a year and 37 out of 43 areas across the UK are exceeding legal EU limits of the key pollutant, nitrogen dioxide, much of which comes from diesel engines.

Volkswagen admitted in September 2015 that almost half a million of its diesel vehicles in the US were fitted with software to switch engines to a cleaner mode when they were being tested for emissions.

The manufacturer said 11m of its vehicles were affected worldwide – including almost 1.2m vehicles in the UK.

Areeba Hamid, a transport campaigner for Greenpeace UK, said buyers were responding to negative sentiment around diesel.

“The drop in the sales of diesel cars is no accident, and it is happening all over Europe,” she said.

“People are consciously choosing to buy cleaner vehicles as they no longer want to be complicit in our cities’ pollution problem and condemning our children to the health impacts it causes.

“But car companies remain incorrigible, still selling us brand new diesel cars that pollute up to 15 times more than they are supposed to.

“Cleaner technology exists. Instead of lobbying for weaker standards and gaming tests, car manufacturers need to ditch diesel altogether and go electric.

“This data shows that buyers are beginning to do just that, what are the car manufacturers waiting for?”

Jim Holder, the editorial director of What Car? magazine, said he was surprised by “the scale of the drop-off” in demand but he thought drivers may be responding to uncertainty about future regulation.

He said: “There is no clear government strategy on diesels. There has been a wave of negative headlines around the fuel but at the same time the taxation system continues to incentivise them.

“These mixed messages do nothing for consumer confidence, nor does the blanket reference to all diesels being dirty. There have been significant steps in reducing emissions, particularly with the latest Euro 6 regulation compliant units that are on sale now.”

Last month the government published long-awaited plans to improve air quality, including a “targeted” scrappage scheme to take the most-polluting vehicles off the road.

Clean-air zones are being established in several towns and cities across England, which could involve charges for the oldest and dirtiest vehicles. The most polluting vehicles will be forced to pay up to £24 a day to drive in central London from 2019 under plans unveiled by the mayor of London, Sadiq Khan.

Holder predicted that sales of diesel cars will continue to suffer while there is uncertainty over future policy.

He said: “Until there is clarity over where future tax incentives will lie, and what city centre charges will or won’t be imposed, diesel sales will remain under pressure.

Greg Archer, the clean vehicles director at campaign group Transport & Environment, said buyers also had one eye on the depreciation in value that diesel cars could suffer.

“The sales figures show drivers are losing faith in dirty diesel and are beginning to turn to clean electric alternatives,” he said.

“Drivers know resale values will be rock bottom in a few years time as more towns ban or charge diesels to enter. Carmakers need to recall and repair these polluting monsters that continue to poison both the air and their reputation.”

In May registrations of new petrol cars rose by 0.4%, while demand for alternatively fuelled cars increased by 46.7%.

The overall new car market fell by 8.5%, the second consecutive month of decline. Many buyers brought orders forward to March ahead of new vehicle excise duty rates coming into force which mean the vast majority of new cars now incur a larger fee.

The SMMT’s chief executive, Mike Hawes, said: “We expected demand in the new car market to remain negative in May due to the pull-forward to March – which was an all-time record month – resulting from VED reform. Added to this, the general election was always likely to give many pause for thought and affect purchasing patterns in the short term.”