Lifeboats have been ordered to limit their speed to 20 knots during non-emergency callouts and training exercises after the RNLI saw its fuel bill rise from £1.5m in 2007 to an estimated £3m this year.

Worldwide oil prices have retreated since their peak at $147 a barrel in July, but they remain high, currently sitting at $119 a barrel, compared to $73 a year ago. This has severely impacted the RNLI's running costs.

The RNLI has insisted that emergency calls would not be affected and some high-speed training would still take place.

"Everybody knows about fuel efficiency with their cars. So what we can do with lifeboats is drop back to 20 knots on non-emergency operations to save fuel," RNLI divisional manager Barry Wagstaff told Sky News.

"The coxswains are educated and disciplined in this but ultimately they make the decision - if there's someone in trouble, if they get a shout, then it's business as usual."

A single Trent Class lifeboat uses 360 litres of fuel an hour at its top speed of 24 knots, but only 100 litres an hour at 20 knots.