London: Thousands of confidential documents lost by the Serious Fraud Office have turned up at a cannabis farm, it emerged last night.

The fraud squad last month admitted it had lost 32,000 documents, 81 audio tapes and other electronic media from 59 sources after accidentally putting them in the post.

The data included the identity of a major prosecution witness in a £43 billion (Dh249.88 billion) fraud case against defence giant BAE Systems. But now it has emerged the files were put in a self-storage warehouse in London’s Docklands, which was also used to house stolen goods and grow cannabis.

Shadow attorney general Emily Thornberry said she was “profoundly shocked” after being told about the epic blunder. It is the latest in a long list of episodes that have called into question the competence of the fraud office, which receives £31 million of taxpayers’ money annually. The Daily Mail last month exposed SFO bosses for negotiating ‘irregular’ pay-offs in secret for executives worth £1 million.

Thornberry, the Labour MP for Islington South and Finsbury, said: “They sent it to the wrong person, who put it into storage. I understand there was stolen property in the warehouse, and there was also a cannabis factory. You couldn’t make it up.’

In a written parliamentary answer to Thornberry, solicitor general Oliver Heald revealed the SFO had spent more than £10,000 finding the files. It claims it has recovered 98 per cent of them.