Van Buitenen, an internal auditor, made allegations of massive financial mismanagement within the commission late last year, prompting former president Jacques Santer to set up a Committee of Experts to review financial controls.

The move backfired when the committee discovered that huge amounts of money had gone missing and a dearth of auditing procedures to track the spending. All 20 commissioners resigned in March.

Van Buitenen, still to return to work since his suspension in January, has also been asked to supply written evidence to support the second Committee of Experts report - into the conduct of senior EC officials, due to be published on 9 September.

Since his suspension, he has been accused of circulating sensitive material to outside parties. His suspension was only lifted when the maximum four-month disciplinary period expired following which he was given a job that he felt did not match his qualifications.

Van Buitenen has since been invited back to the internal auditing department but he has asked for some time to consider his evidence.

For their part, senior commission officials have sought assurances from him that he make no further disclosures that could damage the reputation of the commission.

Martine Reicherts, a spokeswomen for Jacques Santer, said internal commission rules required it to seek guarantees about confidentiality. 'If you have confidential information you should go to your superiors,' she said.

Guy Dehn, director of UK-based whistleblowing organisation Public Concern at Work, condemned van Buitenen's treatment. 'He has been asked to give evidence but he has been quite worried about it and he has had a number of letters from the commission saying that they will bring fresh disciplinary charges while the old ones are still going on,' he said.

Dehn said if Brussels introduced legislation like the new UK laws designed to protect whistleblowers taking effect on July 2, officials would be unable to act against van Buitenen.