Former Tory MEP Den Dover, who was expelled from the Conservative Party over allegations of expenses misconduct, has been ordered by the European Court of Justice to repay £345,289 in "unjustified" claims.
Mr Dover, 72, an MEP for the North West England region from 1999 to 2009, was suspended and then expelled from the party in November 2008 for "gross misconduct" after the Parliament demanded repayment of £538,000 in allowances officials said should not have been claimed.
He stood down at the 2009 European elections and launched an appeal in the European Court against the decision by European Parliament administrators to seek the return of the cash.
The Luxembourg judges found that he should pay back part of the amount - but said the European Parliament had not sufficiently demonstrated that the rest was unjustified.
The MEP has denied any wrongdoing over expenses he claimed between 1999 and 2008, when a total of £959,446 went to a company called MP Holdings Ltd, which names Mr Dover's wife and daughter as directors.
The money came from allowances MEPs receive to pay the salaries and costs of an MEP's staff.
In 2008 the Parliament's secretary-general raised questions about a possible conflict of interest and asked for full details of the use of parliamentary funds claimed by Mr Dover.
A ruling followed that only £421,156 could be justified in salaries, national insurance and legitimate staff travel expenses. The rest was "without justification" said the Parliament, and it asked for the balance of £538,290 back.
Mr Dover told the court it was up to the Parliament to prove that the payments were unjustified, pointing out in court submissions that "the requirement to provide documentation justifying each item of expenditure since 1999 did not exist when the relevant expenses were incurred".
He said the European Parliament was aware that his wife and daughter held managerial positions in MP Holdings, and claimed that it has never "implemented a transparent system setting out clear preconditions for reimbursement of parliamentary assistance expenditure or required Members to produce documentary evidence of their parliamentary assistance expenditure".