Britain's decision to increase aid to elements of the Syrian opposition reflects a growing worry in UK, American and Israeli intelligence circles over Islamic radicalisation of the anti-Assad revolution.

The Foreign Office announced last week two new decisions on Syria. The first was to triple its "non-lethal" aid to opposition groups within Syria to around £5m. The second was to establish official contact with the political wing of the Free Syrian Army (FSA) for the first time.

Until now, most of the links the British and US governments have had with the opposition was through the Syrian National Council (SNC) but over the last few months, they have gradually become disillusioned with it, partly because of reports that jihadist groups are fighting under its umbrella.

A Foreign Office official confirmed that there was a concern that UK aid and equipment could reach radical groups and therefore "it is being distributed only to groups we are already familiar with."

Israel is also concerned about chaos after the Assad regime's downfall. Its chief worries are the fate of the chemical weapons stockpile currently controlled by Assad's forces and that jihad groups will use Syria as a launching ground for attacks on Israeli territory.

Senior IDF officers have warned that the border with Syria, which for nearly 40 years has been Israel's quietest frontier, could become another battleground like Sinai.