Lord Hutton has launched an inquiry into the source of the leak after the Suns political editor Trevor Kavanagh obtained details of the report prior to its publication.

A spokeswoman for the TSO said that it would fully co-operate with Lord Huttons investigation into the leak as well as conduct an internal inquiry.

TSO stands by its procedures and can confirm that for all staff involved in the publication of the Hutton report, TSO followed the strict vetting procedures approved by HM government, said the spokeswoman.

She added that that there was no evidence to suggest that its security measures had been breached and that all relevant staff had signed the Official Secrets Act.