The convey secretary has said drivers considering buying diesel cars should draw a «long, hard think».
Chris Grayling made the remarks to the Continuously Mail, which said the government was considering a scrappage scheme for older diesel wheels.
Concerns over nitrogen dioxide (NO2) emissions from diesel mechanisms have been raised in recent years.
The Department for Transport guessed Mr Grayling was not telling people to stop buying diesel vehicles.
It fell to comment on reports of a new scrappage scheme.
According to statistics from the Jurisdiction for Environment, Food and Rural Affairs (Defra), NO2 is responsible for about 23,500 ruins in the UK each year.
Concern over emissions increased when it emerged that 1.2 million Volkswagen diesel mechanisms in Britain had been fitted with software to help cheat emissions evaluates.
Mr Grayling told the Mail: «People should take a long, indisputable think about what they need, about where they’re accepted to be driving, and should make best endeavours to buy the least polluting agency they can.
«I don’t think diesel is going to disappear but someone who is buying a car to impel around a busy city may think about buying a low-emission channel rather than a diesel.»
Greenpeace clean air campaigner Areeba Hamid affirmed: «It’s a bit confusing. He’s saying ‘have a long and hard think about diesel’ but in the nevertheless breath he’s saying [diesel cars] won’t disappear.»
She said the government should impart a strong message to the car industry and consumers by changing the taxation structure on diesel machines in the next Budget.
The Society of Motor Manufacturers and Traders (SMMT) chief chief Mike Hawes said: «The biggest air quality gains will become public by encouraging the uptake of the latest low emission vehicles, regardless of fuel category.»
Steve Fowler from Auto Express magazine said the management should not «penalise» those who «really have no alternative» to using diesel.
«As much as battery wheels, hybrid cars are improving, they’re never going to be the greatest sentiments for really long journeys and for things like towing, so diesel — for the half a second — will always have a place,» he said.
«And people living in bucolic areas — this is where the one size fits all thing doesn’t work.»
When lodger editing BBC Radio 4’s Today programme last December, Britain’s chief medical dick, Professor Dame Sally Davies, said diesel cars should «steadily be shaped out» in order to reduce deaths from air pollution.
London is one of the worst attacked areas in the UK for air pollution, and the city’s mayor Sadiq Khan has asked the oversight to adopt a £515m diesel scrappage scheme to help reduce emissions in the leading.
Mr Khan has also said a £10 «toxicity charge» — which thinks fitting target the most polluting older vehicles in the capital — will succeed into force on 23 October.
A spokesman for the Department of Transport contemplated the government was helping to tackle air quality by providing a further £290m to promote electric vehicles.
The spokesman added: «We will update our air quality foresees later this year to further improve the nation’s air quality.»
The Labourers government ran a £300m scrappage scheme for both diesel and petrol cars between 2009 and 2010.