The NHS has been forced to spend nearly £65 million to make hundreds of ambulances compliant with London Mayor Sadiq Khan's Ulez scheme.
Under Ulez, drivers must pay £12.50 a day to drive in the capital if their vehicle fails to meet emissions standards.
It was expanded to cover the whole of Greater London in August.
Freedom of Information requests sent to NHS ambulance services in the South of England reveal the agreements made with Transport for London that exempt them from the expanded Ulez for a short period while their fleet is made compliant.
Each vehicle costs £140,000 to replace. The South East Coast Ambulance Service has until October 2025 to replace 279 vehicles.
The London Ambulance Service said 27 per cent of its frontline fleet is not compliant, so 255 vehicles need replacing.
The charge has also hit staff and patients travelling to hospitals in the zone in non-compliant vehicles.
Following the Uxbridge result, Labour leader Sir Keir Starmer said that Mr Khan should 'reflect' on ULEZ due to the 'impact it's having on people'.
Tory chairman Richard Holden said: ''These revolutions are shocking - even by Mayor Khan's standards.
'Taxing hardworking people to simply drive their cars was bad enough - but Mayor Khan ham-mering our NHS ambulance services with tens of millions of pounds of extra cost, just to do their job and get to patients to hospital is downright disgraceful.
'The taxpayer should not be forced to swallow the cost of another one of Sadiq Khan's ideologi-cally obsessive vanity projects.'
Susan Hall, the Tory candidate for next year's mayoral election, said: 'These eyewatering sums show another cost of the ULEZ expansion that Sadiq Khan would rather ignore.
'When our NHS is forced to spend tens of millions to comply with Sadiq's tax-grab plan, surely the Mayor needs to fess up and admit that he's got it wrong? But we know he won't.
'He's ignored Londoners, he'll ignore everyone else - I am determined to see him out of office in May, and his ULEZ expansion will be gone on my first day as Mayor.'
A spokesman for Mr Khan said: 'The Ulez is about saving the NHS money in the long term.
'If no further action is taken to reduce air pollution, the cost to the NHS and social care system in London is estimated to be £10.4 billion by 2050.'