Two Sea King search and rescue helicopters are based at Chivenor
RAF search and rescue helicopters based in north Devon will only be available during the day, a minister says.
The Ministry of Defence is planning to cut the service at RMB Chivenor from 24 to 12-hour cover from 2012, Defence Minister Quentin Davies said.
In a letter to Cornish MP Andrew George, Mr Davies said future night-time cover was be provided by just nine bases around the country, down from 12.
RMB Chivenor will be downgraded to day-time cover only, he said.
Mr Davies said that the move would coincide with a fleet of new rescue helicopters coming into service that were faster than current aircraft.
He said: "In light of the capability of these new helicopters, we have been able to conclude that we can continue to provide effective and responsive coverage for all night-time incidents utilising only nine of the 12 bases.
"Additionally, historical data shows that the level of incidents falls markedly from the daytime peaks."
He said that Portland in Dorset, which is already a daytime-only service, RAF Boulmer in Northumberland and Chivenor would be 12-hour bases.
He said: "This will still enable us to meet, and indeed exceed, previous historical concurrency and surge incidents levels at night-time across the UK, when we transition in to the new service from 2012."
Two Sea King search and rescue helicopters of the RAF's 22 Squadron are currently based at Chivenor.