Three British helicopters sent to help with rescue efforts in Nepal following a devastating earthquake are to return without being used, the British government said on Saturday.

Two major earthquakes have hit Nepal within three weeks, leaving almost 8,500 people dead and leaving huge numbers without shelter.

"We are disappointed that our Chinooks will not be supporting the World Food Programme's request for help in distributing aid," a government spokesman said.

The three Royal Air Force Chinook helicopters had not reached Nepal but were stranded in Delhi, India, for a week after being sent to bring supplies and rescue stranded victims after the first quake on April 25.

"All decisions on the relief effort are ultimately for the government of Nepal and they have advised that there is no need for the Chinooks to remain forward-based in Delhi," the spokesman said.

The Nepalese government has said it was overwhelmed by the scale of the first earthquake, the deadliest to hit the country in over eight decades.

On Friday, the United Nations renewed calls for assistance to help victims stranded in remote areas accessible only by foot or helicopter, saying the implications of not acting quickly would be "severe".

"We can only expect misery, a crippling loss of dignity and the real potential for more deaths, especially in the rural and remote areas," Jamie McGoldrick, UN humanitarian coordinator for Nepal, said in a statement.

He called on donors to dramatically increase their aid contributions, which have reached 14 percent of the $423 million appeal.

Britain said that it had contributed over �23 million ($36 million, 31.5 million euros) in aid and that it would continue to support the relief effort.