In a talk at Britain's House of Commons on Thursday, Brig-Gen Aqil Hashem said more than 15,000 people had now been killed in Syria, and that the only way out of the conflict was for the world's militaries to intervene.

Speaking to a packed audience of MPs, diplomats, journalists and others at a seminar hosted by the Henry Jackson Society think-tank, Gen Hashem said the very minimum the world needed to do in Syria was to carve out a militarily protected "safe zone" in north-west Syria, similar to the one made for the Kurds in northern Iraq in 1991.

Gen Hashem, who served for 27 years in the Syrian army, including in three wars, said that ideally, he would welcome the sort of full-scale military intervention seen in Libya last year, but added that he appreciated there was little appetite for that.

Air strikes

Instead, he suggested that targeted air strikes by unmanned aerial vehicles (UAV) against the regime's "150 intelligence and security bases across the country" would be sufficient to demoralise many key figures into defecting and thereby break the regime's will to survive.

Gen Hashem, who said he was in daily contact with a wide range of sources inside Syria, said he was well aware of the arguments against military intervention, including the risk of a sectarian civil war, the proliferation of weapons and the creation of unregulated militias.

But using the delayed international intervention in the Balkans in the 1990s as an example, he said: "The more we delay this intervention, the more likely those risks are to come true."

"For the first seven months of the Syrian uprising," he said, "the demonstrations were peaceful, and yet 5,000 people were killed by the regime then." Today, he puts the death toll at over 15,000, with 80,000 injured and countless numbers missing.

"I believe it is the utmost evil genocide in Syria," he said. "The regime is killing its own people."

Gang-raped

The former army officer recounted to a shocked audience a recent case in the city of Hama in which, he said, 46 people from an extended family were rounded up by plainclothes thugs known as shabiha.

Widespread torture, he said, is being practised by the regime, not for information gathering, but for reasons of "hatred and enjoyment".

But Gen Hashem, when questioned by his audience, gave a hint of the disunity and fractiousness that plagues the Syrian opposition.

It was clear he had fallen out with some key figures and he accused the opposition Muslim Brotherhood of fomenting problems inside both the political and military rebel groups, saying "they are only following their own agenda, rather than working for the common cause of bringing down this regime".