The committee was meeting on Tuesday morning to decide whether to call the head of the Foreign Office, Sir John Kerr, to give evidence again in the light of his refusal to answer certain questions on previous occasions.

Sir John has said that he could not answer some points while the Legg inquiry into the affair is continuing and last week said he had been told by Mr Cook to remain silent. The committee is also angry that Mr Cook has not handed over telegrams which it wants to examine.

Cook letter accuses committee

As the committee was about to sit in private session, however, it received a letter from the Foreign Secretary essentially arguing that it should pick on someone its own size, describing as "unfair" and "unreasonable" the continuing questioning of his officials.

"If the select committee wishes to persist in putting questions on these matters, they must put them directly to myself as head of the Foreign and Commonwealth Office and not to officials who are accountable to me," Mr Cook wrote.

He said it was the collective view of the government that a parrallel inquiry by the committee would be prejudicial to the Legg inquiry, adding that Sir Thomas Legg agreed with this view.

Mr Cook repeated that ministers and the Foreign Office had done nothing wrong and had not been involved in the shipment of arms by Sandline International to the ousted President Kabah of Sierra Leone.