Sir John Kerr, who was recalled to the House of Commons Foreign Affairs Committee after being forced to retract evidence given at an earlier hearing, said he could say little until an inquiry was complete.
The Permanent Secretary to the Foreign Office did confirm, however, that two Foreign Office ministers were given different information about the involvement of a firm of British mercenaries in a counter-coup.
Baroness Symons of Vernham Dean and Tony Lloyd had answered parliamentary debates on consecutive days in March, but while Mr Lloyd was not told that there was a Customs and Excise inquiry into the activities of Sandline International, Baroness Symons was.
Sir John Stanley, Conservative MP for Tonbridge and Malling, said the committee had taken advice from the clerk of the House of Commons and that Sir John Kerr would be in contempt if he failed to answer questions.
But the official told the committee several times that he could not help them because of an ongoing inquiry by Sir Thomas Legg into whether officials or ministers knew about Sandline's activities.
The company was paid by the exiled Sierra Leonean President, Ahmad Tejan Kabbah, to help reinstate him last March.
Sir John Kerr said that to give new information might prejudice any possible disciplinary proceedings, over which he would preside as head of the diplomatic service. He told the committee last month that Mr Lloyd had been briefed about the Customs and Excise investigation before he answered a Commons' debate. Later the same day, he was forced to retract the evidence that he had given about Mr Lloyd.
Yesterday, though, he was reluctant even to repeat his earlier statements.
He said: "I don't believe it is right for us to go further until all the aspects have been explored by the independent investigation. I am very, very uneasy about pursuing the matter now."
Sir John Stanley told him: "With great respect, you are taking yourself into very serious country indeed. It is unacceptable to refuse to answer a question put to you directly related to your previous evidence. It is simply not acceptable to give non-answers."
Sir John Kerr was asked to reconsider his position, and could be called back before the committee yet again.
David Heath, the Liberal Democrat MP for Somerton and Frome, said afterwards: "If he wants to be before our committee for the rest of his life answering questions on Sierra Leone, this is the best way of doing it.
"As far as we are concerned the Legg inquiry is not a judicial one and we are perfectly entitled to ask whatever questions we choose," he said.
The committee will contact Robin Cook again to demand that he hands over a series of telegrams which he has already refused to let them see.Reuse content