In a note to his staff, Mr Staple said he did not think there was evidence they had done anything wrong, but he said: 'Unguarded words damage the reputation of us all.'
His move came after Sir Nicholas Lyell, the Attorney General, privately made it clear at Westminster that, in spite of assurances by Mr Staple, he wanted the SFO director to read the riot act to his staff.
The Attorney General's intervention followed protests by Michael Mates and other Tory MPs that the timings of raids by the SFO were leaked to the press, damaging the share-value of the companies they were investigating.
The Attorney General had privately told colleagues he was deeply concerned about the behaviour of police and accountants seconded to the SFO for its raids. He let it be known yesterday he would be telling the SFO to stop the leaks.
It also emerged yesterday that the Attorney had asked Sir Robin Butler, Cabinet Secretary and head of the Civil Service, to investigate allegations that MI6 was involved in a plot to destabilise the economy of northern Cyprus through the collapse of Asil Nadir's Polly Peck empire.
Sir Nicholas asked Sir Robin to investigate the claims passed to him by Mr Mates, then a Northern Ireland minister, at a meeting at the Attorney's chambers on 10 May this year, referred to in the letters published by Sir Nicholas yesterday.
Sir Nicholas rebutted the charge against MI6 in a letter to Mr Mates dated 8 June. 'Your more general assertions on collusion to undermine Polly Peck were unsupported by any evidence. They are categorically refuted by the relevant authorities.'
The Independent has learned that before replying, Sir Nicholas asked Sir Robin to raise the allegations with MI6. Sir Robin did so, and assured Sir Nicholas there was no evidence. However, Sir Nicholas did not inspect the evidence himself.
The possibility of MI6 involvement in the Nadir affair will strengthen demands for the intelligence and security services to be brought under democratic oversight by a Commons committee.
However, Sir Nicholas is determined to resist demands for an inquiry into the operation of the SFO, deflecting the pressure by pointing out that a review is being carried out by the Home Affairs committee of the Commons under a Tory chairman, Sir Ivan Lawrence QC.
The letters arrived in three large boxes delivered to the vote office in the member's lobby of the Commons.
A senior member of the 1922 Committee said most Tory MPs were uninterested. But he said there was concern at the reports that the suspended Inland Revenue official, Michael Allcock, had passed information to the Stock Exchange Insider Trade Unit, which passed it to the SFO.
The Attorney General has told colleagues that the disclosure does not amount to a breach of the law because the SFO collected its information from the Stock Exchange.
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