Liam Fox asked Ministry of Defence (MoD) officials to provide his friend Adam Werritty with details of his diary during foreign visits, it was revealed today.
The practice was disclosed by MoD Permanent Secretary Ursula Brennan in her interim report to Cabinet Secretary Sir Gus O'Donnell on contacts between the Defence Secretary and Mr Werritty.
The Defence Secretary had accepted that this was "not appropriate", she added.
"During the course of the review it has become apparent that the Defence Secretary provided or asked his office to provide some diary details to Adam Werritty, in connection with visits where Mr Werritty was to be present," she said.
"In the next phase of the review I will confirm this from email records.
"Dr Fox has accepted that it is not appropriate to ask officials to provide ministerial diary information to a third party."
She added that she would be making clear to all private offices that diary and travel information should not be shared with third parties other than ministers' wives or partners.
It also emerged in her interim findings that Mr Werritty had been present for a meeting between Dr Fox and the then forthcoming Israeli ambassador.
"Dr Fox acknowledges that it was not appropriate for Mr Werritty to have attended such a meeting at the MoD," the top civil servant wrote.
That had been one of only four of Mr Werritty's visits to the MoD during which other people were present.
There were two meetings, attended by a Private Secretary and Special Adviser, when diary arrangements for Dr Fox's lecture in Sri Lanka had been discussed.
The other was when Mr Werritty accompanied some Sri Lankans he had helped to arrange a discussion with the Defence Secretary.
In total Mr Werritty had been in the MoD 22 times according to visitor logs, although Ms Brennan said she could not "exclude the possibility that there may have been a visit which for whatever reason was not recorded in the logs".
Officials believed that Mr Werritty's visits were "largely personal conversations" with Dr Fox.
"I have spoken to the Principal Private Secretary and other members of the Private Office staff; they believe that Adam Werritty's visits to the Main Building were largely personal conversations with the Defence Secretary," she wrote.
"They are confident that the Department did not provide Mr Werritty with classified papers or briefings.
"This is confirmed by Dr Fox, who pointed out that while on most occasions Mr Werritty came to his office, there were occasions when the two met in the Pillared Hall coffee bar in the MoD Main Building."
Ms Brennan said Dr Fox's Dubai meeting with Harvey Boulter, chief executive of private equity firm Porton Capital, was an example of a "grey area" in the arrangements of ministers' overseas visits.
She said personal or party political meetings, at which the minister is not accompanied by a civil servant Private Secretary, "can potentially stray into government business".
"The evidence suggests that there has been at least one occasion (the meeting with Harvey Boulter) when the Defence Secretary had a planned meeting on MoD business, due to take place during free time," she said.
"The nature of this encounter was not known to the Private Office and therefore they did not arrange to have a Private Secretary present.
"To avoid this happening again, Private Offices should ensure that their Minister is clear that any meetings or visits due to take place during personal time should not touch on government business."
She added that where there was any risk that a meeting might "stray into" Government business then an official should be present.
Mr Werritty's use of business cards describing himself as the Defence Secretary's "advisor" was raised by Ms Brennan with Dr Fox on August 23 after a story in The Guardian.
"Dr Fox confirmed that he had already dealt with the problem and that it was wrong for Mr Werritty to have used such a card," she said.
The Defence Secretary had told her in recent days that he "thought he first knew of it in June, and that this was when he had told Adam Werritty to stop the practice".
"This is confirmed by one of the Special Advisers, who recalls becoming aware of the problem in June, possibly as the result of an earlier press comment," Ms Brennan said.
"He recalls that immediately after this the Defence Secretary and the Special Advisers held a meeting with Mr Werritty at which Dr Fox told Mr Werritty that this was unacceptable and he must stop issuing the business cards."