Tens of thousands of electronic searches have been conducted under a secret US programme to monitor global financial transfers for signs of terrorist activity, the official in charge of the programme has told the Financial Times.

Stuart Levey, the under-secretary for terrorism and financial intelligence at the US Treasury, said a “very small number” of these searches related to companies suspected of being fronts for terrorist organisations, but the vast majority related to individual terrorist suspects. He said it had been a “very, very powerful” tool in the struggle against terrorism.