A cancelled Panorama investigation into Lord Ashcroft discovered that the peer's company, BCB Holdings, broke Stock Exchange rules by failing to declare a string of business interests held by one of its most senior directors.
Documents uncovered by the BBC in the Caribbean revealed that Philip Osborne, a long-time associate of the Tory donor, held undisclosed directorships in several companies in the Turks and Caicos Islands, where BCB controls the biggest bank.
The BBC pulled the broadcast hours before it was due to air on Monday, after Lord Ashcroft's lawyers challenged one of the main allegations in the programme. The BBC said it was examining new information and would consider a future broadcast.
Mr Osborne has been company secretary of BCB since 1993 and became a member of its board in 2007. London Stock Exchange rules require new directors to declare "without delay" the names of all companies and partnerships of which they are a director, or have been a director in the previous five years.
Mr Osborne declared 27 current directorships in February 2007, but the list was not complete. Missing were two Turks and Caicos businesses, Sun Rise + Set and Emerald Point, which he had joined as a director four months earlier with Rodney Propps, a resort developer. Panorama also discovered another company Mr Osborne joined later in 2007, Emerald Point Resort, that was not disclosed to shareholders.
BCB disclosed the existence of four directorships held by Mr Osborne – including Sun Rise + Set and the Emerald Point companies – last week after Panorama took its evidence to the London Stock Exchange and to Cenkos, BCB's financial adviser.
A spokesman for the Stock Exchange said it had "noted the corrective announcement", but declined to comment further. The Exchange is able to fine companies and directors who breach its rules, and to issue a public or a private censure. It is not expected to take any action in the BCB case, which it is understood to view as a minor breach. Lord Ashcroft's representatives did not respond to questions on the matter.