It will fuel demands by Labour MPs that the former trade and industry secretary should remain on the back benches for a lengthy period. It will also surprise many observers, because reports a week ago quoted "friends" of Mr Mandelson saying he had been reassured Commons rules did not require him to register the loan.
In fact, no such judgement has been made. He has asked for advice and been told he should register the interest, which he has done but an investigation on whether he broke the rules is under way.
Mr Mandelson and Mr Robinson, who was paymaster-general, resigned before Christmas when details of the loan became public.
Ms Filkin reports to MPs on the Standards and Privileges Committee in two weeks on the complaints about the loan. One is from the shadow trade secretary, John Redwood, and two from members of the public.
The complaints also address the question of whether Mr Mandelson should have registered flights he took in the jet of an American lingerie millionaire, Linda Wachner. He has said he did not need to declare them, because they were in a personal capacity and had nothing to do with his work. The rules say overseas visits must be registered if they relate in any way to membership of the Commons.
Mr Mandelson has also said the loan did not need to be registered because it was an arrangement between MPs. The Commons rules do not specifically mention such arrangements. In 1996 the then standards commissioner, Sir Gordon Downey, ruled that preferential treatment on loans to the Tory MP Roy Thomason should have been listed. MPs on the Standards and Privileges Committee will decide whether Mr Mandelson should be punished and how severely.
Ms Filkin has said that she wants ordinary people to feel they can approach her about MPs' conduct.
Last night Mr Redwood said he was sure Mr Mandelson had broken the rules. "Everyone believes that Mr Mandelson borrowed money on terms that are not normally available commercially, so surely the inquiry must find that he is guilty of failure to make a declaration.
"I also hope Mr Mandelson will explain how many other flights he received and why he did not think they were worth declaring," he said. A spokesman for Mr Mandelson said the commissioner's inquiry was old news and the impression that he had been cleared was the fault of misinterpretation by the media.
r Mr Mandelson could have received more than pounds 15,000 in severance pay after resigning from the Cabinet, the Government said last night.
The Secretary of State for Trade and Industry, Stephen Byers, confirmed in a Commons written reply that under government rules his predecessor had received a pay-off of a quarter of his annual salary as a minister.Reuse content