Britain's armed forces will focus on stamping out potential insurgencies in hotspots of extremism after next year's withdrawal from Afghanistan, the head of the military said in an interview published Monday.

General Nicholas Houghton, who took over as chief of the defence staff in July, also hit out at critics of the army's restructuring plans, calling them "salivating defeatists".

The army is undergoing a programme that will see it reduced from 102,000 regular troops to 82,000 by 2020 as the government seeks to cut a public spending deficit.

The Territorial Army, Britain's volunteer active-duty reservist force, will be boosted by 10,000 members under the plan.

"Those who, three months into a five-year recruiting exercise, appear to be salivating at the prospect of failure, would be better to stay quiet because they are doing us no favours at all," he told the Times newspaper.

"Personally, I have no doubt that we will get there."

Britain currently has around 8,000 military personnel in Afghanistan, ahead of a full withdrawal by the end of next year.

Thousands of troops are also due back from barracks in Germany, which were established following World War II.

Houghton explained that staff would be strategically deployed to head off potential conflicts in areas currently at risk from extremism.

"Our best interests as a nation are served by the maintenance of... stability. It's a different and softer and more cunning use of military capability," he said.

"We have West and East African training missions. There is more that we can yet do in Somalia.

"We have a similar mission in South Africa... and we are embarking on a range of other relationships with Gulf States, in the Far East," he added.