By Andrew Osborn
LONDON, Dec 18 (Reuters) - The head of Britain's armed forces said on Wednesday his country had become sceptical about projecting military force around the world after two back-to-back wars, urging Britons not to lose what he called their "courageous instinct".
Speaking just over three months after the British parliament voted against military action in Syria, General Nicholas Houghton's comments reflect anxiety in the armed forces about what they view as a growing political and public reluctance to use them to intervene in global hot spots.
Military chiefs are concerned military inaction could threaten Britain's global reach and undermine their own ability to protect and increase an already reduced defence budget at a time of fiscal austerity.
"The UK's armed forces have never, in the 40 years I have known, been held in such popular high regard," Houghton told the Royal United Services Institute (RUSI) in a speech in London.
"But the purposes to which they have most recently been put has seldom been more deeply questioned. As a nation we have become a touch sceptical about the ability to use force in a beneficial way."
British troops helped topple Saddam Hussein in Iraq and have spent 12 years fighting the Taliban in Afghanistan, a country they are due to leave by the end of next year.
Yet polls show the British public is sceptical about what those interventions achieved and Prime Minister David Cameron's shock failure to win parliament's approval for a limited military strike on Syria prompted a bout of hand wringing about the former imperial power's role in the world.
Houghton said one of his biggest challenges was to try to "re-validate" the use of military force in the minds of government and the wider public, saying he had watched French forces intervene in Africa recently with admiration.
"The final part of the paradigm has the potential to become the most damaging of all," he said.
"It is the creeping aversion to risk in the employment of our armed forces. We must be careful as a society and as a professional military not to lose our courageous instinct since it is one of the things which keeps us in a class-apart."
With a military budget of $61 billion, Britain was the world's fourth largest spender after the United States, China and Russia in 2012, but the Conservative-led government has cut expenditure and jobs to try to tackle a large budget deficit.
Houghton said the government would have to recalibrate its defence strategy at some point because if it remained unchanged the country would receive "exquisite equipment", but not have enough people to man that equipment or train on it.
Britain's Royal Navy was "perilously close" to having such staffing problems, he said. (Editing by David Evans)