That pounds 12.75m trust, called Orion, is based in Guernsey. But Mr Robinson also put over pounds 300,000 worth of shares in a family company into a trust in Bermuda, another secretive tax haven. The shares in Latchuser Limited, a Robinson property business, were transferred to the International Trust Company of Bermuda, a firm specialising in administering trusts for wealthy individuals, in 1991.
Since the IoS disclosed he was a discretionary beneficiary of a pounds 12.75m trust for his family in Guernsey, Mr Robinson and his Labour minders have battened down the hatches. Now attention has turned to Joska Bourgeois, the wealthy Belgian woman who set up Orion for him and his family in Guernsey. According to accepted wisdom - and a story that is not denied by Mr Robinson - she made her money from importing cars into her native Belgium. But she left pounds 35m in her will when she died three years ago. To have earned that sum from selling luxury foreign cars in a country as small as hers would have been remarkable.
A flamboyant former model, she built up a business, International Motor Company, which was sold for pounds 80m. In 1979, aged 65, she moved from Belgium to Switzerland for tax reasons. She is supposed to have divided her time between there and Cannes. But in Switzerland there is barely any trace of her. It is true, she had an apartment in Saconnex, in Geneva. In the same building she owned an office, registered in the name of the oddly titled firm, for a car dealer, of Etudes Techniques & Economiques.
Inquiries by the IoS in Switzerland show she was totally unknown to local society, despite her wealth and, if the legend is to be believed, apparently spending much of her time there. The main Swiss importer of Jaguar and other British cars for the past 50 years has never heard of her - although he did know Sir William Lyons, the Jaguar founder and the man, apparently, who awarded her the contract to sell the luxury marque in Belgium.
The Swiss dealer, for one, wonders how she could have made so much money from selling Jaguars in Belgium.
The much younger Mr Robinson enjoyed a close relationship with her, becoming a financial adviser-cum-management consultant - this may explain the oddly titled firm in Geneva.
Mme Bourgeois is dead and in her last years her business affairs were withdrawn from public scrutiny. The one person who could shed some light on her and his dealings with her, is, of course, Mr Robinson. But he is saying nothing, apart from the statement he issued in response to questions from the IoS last Saturday. He will not discuss Orion, who its trustees are and which companies, in addition to TransTec - the engineering firm built up with a loan of pounds 100,000 from Mme Bourgeois, that he chaired until becoming Paymaster-General - its money is invested in.
The Conservatives will tomorrow demand he brings all his assets within the reach of the Inland Revenue, or resign as a Treasury Minister. Peter Lilley is to put down a fresh series of Commons questions designed to throw more light on the minister's millions.
"There is a conflict of interest between the minister with interests in an offshore trust who is also making policy on closing tax loopholes," the Shadow Chancellor said yesterday. "Either Mr Robinson must try to repatriate assets he currently has outside British tax jurisdiction, or it is hard to see how he can remain a member of the Government which has said it will not allow millionaires to have off-shore tax havens."
At the Tories' instigation, Sir Gordon Downey, the parliamentary standards watchdog, is investigating whether Mr Robinson should have declared Orion in the MPs' Register of Interests. Mr Lilley also wrote to Sir Gordon after it was revealed that Orion had bought pounds 3m of shares in TransTec since the election.
Mr Robinson's position may also be scrutinised by the Committee on Standards in Public Life, to whose chairman, Sir Patrick Neill, Mr Lilley has also written.
A third investigation may be set in train by the Commons Committee on Standards and Privileges, to which Sir Gordon will make his report.
Additional reporting by Patrick Martin in GenevaReuse content