An MP has criticised plans to expand a pollution charge zone for driving in London, saying it will hit Kent motorists.

More than 200,000 more drivers could be slapped with a £12.50 daily fee for using London's roads after mayor Sadiq Khan announced he will expand a pollution charge zone to boost air quality.

Kent MP Craig Mackinlay, who represents South Thanet, described it as "an appalling decision".

Mr Khan said extending the ultra-low emission zone to cover the whole of the capital from August 29 next year is “one of the toughest decisions I’ve taken”.

This will come after its most recent expansion in October slapped around 80,000 Kent motorists with an £80 fine after driving into the new ULEZ zones.

By area, Medway motorists were most frequently stung with 16,689 fines amassed, followed closely by Dartford (10,320) and Gravesham (7,602).

The scheme, which operates at all times except Christmas Day, is currently limited to the area within the North and South Circular roads.

Transport for London (TfL) estimates that on an average day about 160,000 cars and 42,000 vans that use London’s roads would be liable for the £12.50 Ulez fee.

But the latest move has been criticised by some.

Mr Mackinlay wrote on Twitter: "The same Sadiq Khan who bleats that ‘government should do more’ about cost of living wants to tax outer Londoners and Kent residents... if they aren’t wealthy enough to own an electric vehicle."

Transport officials believe that by the end of next year the expansion of the scheme will have encouraged tens of thousands of those drivers to switch to vehicles that comply with the minimum emissions standards or use other modes of getting around such as walking, cycling or public transport.

Whether or not a vehicle is liable for the charge depends on how much nitrogen dioxide it emits.

For diesel cars and vans to avoid the charge they must generally have been registered from 2016, while most petrol models registered from 2006 are exempt.

Drivers can check the status of their vehicle by entering its registration number on TfL’s website.

Mr Khan described the Ulez as “transformational” and claimed extending it will mean “five million more people will be able to breathe cleaner air and live healthier lives”.

The mayor insisted that the rising cost of living was a “key consideration” in his decision on whether to implement the proposal, which was featured in a public consultation between May and July.

This led to him introducing measures such as a £110 million scrappage scheme to support Londoners on lower incomes, disabled people, small businesses and charities to scrap or retrofit their non-compliant vehicles.

Mr Khan added: “Expanding the Ulez London-wide has not been an easy decision.

“The easy thing for me would have been to kick the can down the road.

“But in the end, public health comes before political expediency.”

Billionaire businessman Michael Bloomberg, who is the UN Secretary-General’s special envoy on climate ambition and solutions, claimed Mr Khan’s leadership is “helping to clean London’s air and set an example for cities around the world”.

But RAC head of roads policy Nicholas Lyes said the announcement will be “a hammer-blow for desperate drivers and businesses already struggling with crippling fuel costs”.