A Foreign Office source said evidence that Iranian authorities are contacting British companies as it tries to circumvent sanctions 'through the backdoor' was a concern. 'We shouldn't be naive enough to know that [Iran] will not try to get these items,' he added.

Among those identified are London businessman Mehrdad Salashoor, who was caught shipping hi-tech navigation equipment adaptable for missile guidance systems to the Iranian military. When the 56-year-old asked British authorities about the licences required to export 11 'gyrocompass' devices worth £650,000 to Azerbaijan he was informed that he would require a special export licence.