It is the first time that the long-suspected link between the Iraqi insurgents and their neighbours has been declared officially by Britain. The United States has for some time been openly accusing Tehran of supporting and influencing the insurgentsâ€™ attacks on coalition troops in Iraq.
Until yesterday the British Government had raised its concerns about Iranian links with the Iraqi insurgents â€œbehind the scenesâ€. One British diplomatic source said this was the chosen method, not least because of continuing moves by Britain and two other European Union partners to persuade Iran to stop its nuclear uranium-enrichment programme.
However, the senior official, speaking anonymously yesterday, blamed Iranâ€™s Revolutionary Guard for supplying the advanced technology that had helped Iraqi insurgents to kill British soldiers with the more lethal roadside bombs.
The most recent death was that of Major Matthew Bacon, of the Intelligence Corps, who died when a roadside bomb was detonated in Basra on September 11, destroying the armoured Land Rover in which he was traveling.
â€œWe think it [the new technology] has come from Lebanese Hezbollah via Iran,â€ the official said.
Yesterdayâ€™s accusations provided further evidence of a steady deterioration of ties between London and Tehran, strained over Britainâ€™s role in Iraq and Iranâ€™s nuclear programme.