The family of missing Gareth David Huntley has expressed sincere thanks to British Prime Minister David Cameron and Defence Secretary Philip Hammond for responding to their campaign seeking to "intensify" the search mission.

The family also thanked the Malaysian government for the efforts to find the Briton, missing since Tuesday (May 27).

In a statement to Bernama here, the family said, "The British Foreign & Commonwealth Office (FCO) told the family they are working with the Malaysian military to quickly escalate the search."

Huntley, 34, went on a trek into the jungle to visit a waterfall in Tioman Island, Malaysia, on the morning of May 27.

He told friends at a nearby charity project office where he was working that he would return by 2pm the same day but has not been seen since.

Gareth’s brother Mark, said: "We're hugely grateful to Mr Cameron and Mr Hammond for their response and their assurances to support the local police with professional searchers who can ensure that GPS mapping and real coordination is available."

Mark added: "FCO have told us they have a good relationship with the authorities will escalate the issue quickly.

"They said that Defence Secretary Phillip Hammond has spoken to the Malaysian Defence Minister Datuk Seri Hishammuddin Hussein who said they are taking it very seriously," he added.

A professional search team is now being deployed, including 10 paramilitary operations commandos, five police officers, three canine guides with two dogs and three civil defence officers.

An eight-strong fire rescue team, two merlin patrol boats, and one helicopter were also deployed.

FCO has appointed local diplomat Karen Song to coordinate the rescue effort from the ground. She arrived in Tioman Island at 10.15am GMT today (Sunday).