The revelation is bound to spark a further official complaint from the Conservatives which could end Mr Robinson's Parliamentary career. Questions will also be asked about whether Mr Robinson, who became paymaster-general in May 1997, should have put the shares in a blind trust under ministerial rules.
The Committee on Standards and Privileges said yesterday that Mr Robinson had broken the rules by failing to register two directorships.
In its report, it delivered an unprecedented warning that one more breach would be "a serious matter". Possible sanctions include suspension from the House or a demand for a second apology. Mr Robinson was forced to make a statement to MPs last November after other undeclared directorships came to light.
The MPs said they were "surprised" that the former minister had not reviewed his entry after earlier complaints. There have already been rumours that Mr Robinson might be planning to leave politics, and further humiliation could prove the final blow.
Research by the Channel 4programme, Mark Thomas Comedy Product found that in April 1997 Mr Robinson became a shareholder in the JCT Property Company, which owned property and unit trusts worth more than pounds 800,000.
Company House records show he and his step-mother, Pauline Robinson, jointly held one third of the shares in the company - listed as "Geoffrey Robinson and Pauline Robinson - PW Robinson Settlement".
Mr Robinson ceased to hold the shares on 3 November, 1997, three months after the post-election deadline for MPs to register their holdings. Nothing in the company's accounts suggest that the former minister received any payment. However, Commons rules show that any beneficial interest in shares greater than 1 per cent of a company or worth more than pounds 25,000 should be registered.
Yesterday the committee upheld complaints by two Tory MPs, David Heathcoat- Amory and Geoffrey Clifton-Brown, which followed earlier reports in The Independent. It found Mr Robinson should have registered directorships of Roll Center Inc, a US engineering firm, and RJ Engineering, a small hi-tech company in the Midlands.
The committee imposed no penalty but hinted it would not be so lenient again. "We would regard it as a serious matter if further instances of non-registration on Mr Robinson's part were subsequently to come to light as a result of a complaint," the committee said. Last year Mr Robinson was criticised by the committee for failing to disclose his interest in the pounds 12m Orion Trust, based in Jersey.
Last night Mr Robinson declined to comment.Reuse content