Peter Mandelson, the Secretary of State for Trade and Industry, has confirmed that his department is examining allegations that Hollis Industries, an engineering company, filed inaccurate accounts when Mr Robinson was a director in 1990.
This follows a complaint by David Heathcoat-Amory, shadow chief secretary to the treasury, who asked the DTI to investigate the matter. Mr Mandelson wrote back that it was "being considered" but that he would "not be able to comment further on any action which the department might take".
Sources at the DTI stressed that the letter was "routine" and did not mean that Mr Robinson would face prosecution. The department always refuses to confirm or deny investigations. However, the development will increase pressure on Mr Robinson, who already faces calls to resign. Last week, he was forced to apologise to MPs after the Standards and Privileges Committee rebuked him for failing to register a business interest.
Mr Robinson was in an earlier row for benefiting from an offshore trust while acting as an adviser to Gordon Brown, the Chancellor, on tax avoidance.