“The Syrian regime is undoubtedly being assisted by the Iranian government in many ways, both the provision of equipment for them and advice on techniques on how to crush protest,” William Hague said.

His comments came amid continuing reports of violence and threats by Syrian forces against protesters. Mr Hague said he was working to get backing for a UN resolution criticising Syria.

But he cautioned that the chances of a UN Security Council agreement were “on a knife edge”.

He went on: “It is an extraordinary example of hypocrisy that the Iranian government, which positioned itself on the side of protests in Egypt and Tunisia, is assisting the Syrian government in actively and brutally suppressing protest and that tells you a great deal about the regime in Iran.”