A former head of Mossad has warned of the increased threat that Israel will face if Bashar al Assad wins the Syrian civil war.

Efraim Halevy, who spoke alongside former MI6 chief Sir Richard Dearlove at a discussion organised by the Zionist Federation in London this week, said that an Assad-dominated Syria would allow large numbers of Iran-backed fighters to mass along the Syrian side of the separation line with Israel. This could “lead to a deterioration with enormous consequences”, he said.

Hizbollah militants have been acting as a proxy army for Iran in Syria by helping Assad combat the anti-regime forces. They have reportedly been assisted by Iranian fighters, including members of the Al Quds force, a foreign operations unit of Iran’s elite Revolutionary Guards.

Mr Halevy said: “Iran sees the Syrian civil war as a test for its status as the hegemon of the Middle East.”

He added that he was not optimistic about the turmoil in the region. “This is a generational conflict, not a regional or local war. It will go on regardless of whether Israel is there or not.”

Sir Richard said that “the disintegration of governments” is crucial to understanding the increased security threats across the region.

“The other big issue is the cold war — now a hot war — between Sunni and Shia. Israel is a victim of a fundamental war of religion which is far from being resolved. In addition, two of the region’s biggest powers are pouring money into their proxy armies.”

Sir Richard said that this proxy war “makes nuclear talks with Iran far more complicated and more difficult to resolve in a satisfactory way. I doubt Obama can achieve an agreement.”