The RNLI has told its lifeboats to slow down to save diesel and the UK's air ambulance services say they need an extra £1m to continue operating at the same level.
Neither the RNLI nor any of the nation's 17 air ambulance charities receive any significant government funding.
"The Government could do a lot more to help air ambulances," said Pat Conafray, income development manager at Thames Valley & Chiltern Air Ambulance Trust, whose fuel costs have risen by £40,000 this year. "We would love it to help us through this difficult stage.
"People don't realise we are a charity. They think we are funded by government."
Air ambulance charities, which fly 17,500 missions a year, pay for all their own costs except the paramedics.
Conafray said government had never embraced air ambulances since the first helicopter took off in 1987 and had come to regard them as "an expensive item off the balance sheet".
The Kent Air Ambulance Trust's fuel costs have leapt from £50,000 to £85,000 since last year.
"It's a very significant hit," said John Tickner, director of operations at the charity. "Somehow we have to find it, otherwise operations will cease, and we can't allow that. We'd like the Government to do whatever it can.
"It's hitting us all. If it gets worse, I'm sure there are going to be casualties."
The RNLI is able to reclaim VAT and hydro-carbon duty on fuel for its 338 lifeboats. But it still expects fuel costs to double from £1.5m to £3m this year.
Hugh Fogarty, head of fleet operations at the RNLI, said it had instructed lifeboat crews on non-emergency missions to adopt a 'twenty's plenty' policy - a bid to save fuel by not exceeding 20 knots.
"Anything to reduce the impact of rising fuel prices would be greatly appreciated," said Fogarty.
A spokeswoman for the Treasury said fuel duty had remained at 50.35p per litre since October.
"The Chancellor postponed the planned increase in fuel duty in April because of concerns about high fuel prices, and has said he is willing to postpone it again in October," she said.
- Charity-run emergency services say the Government should do more to help them with rising fuel costs
- The RNLI has told its lifeboat crews to slow down to 20 knots to save on diesel
- Air ambulance charities say they need an extra £1m to continue operating at the same level
- The Treasury postponed duty rises until October.