Some volunteer drivers who transport NHS patients to and from hospital in Lincolnshire are considering quitting due to a cut in their mileage rate.
Once a driver goes over 10,000 miles in a tax year, the rate drops from 40p per mile to 25p.
Many of the volunteers said they cannot afford to do the job at the lower rate.
More than 100 volunteer drivers help provide the service for NSL, and some attended a meeting on Sunday in Boston to discuss their options.
Spokesman Alan Harvey, who has been a volunteer driver for three years, said the changes would lead to a reduction in volunteers and could affect patients.
“A lot of volunteers say once they’ve reached 10,000 miles they’re not going to drive until the next tax year,” he said.
“We’ve even been stretching it at 40p to really cover the cost of running a car… we don’t mind giving our time up – time is free – but it’s the cost it entails.
“Unfortunately we can’t afford to keep driving at a cost rate… We end up paying for it out of our own pensions.”
Belinda Webb from NSL said the change was introduced after a “diligent review, with patient safety as the overriding objective”.
“Insurance companies are willing to cover volunteer drivers because they recognise what an important role they serve as long they are paid HMRC guideline rates,” she said.
“They are a voluntary service that are highly appreciated throughout the NHS and certainly by us.