The Tories said comments by Jules Muis, who stepped down last month, underlined the importance of the party's campaign to improve political responsibility for tackling fraud.

Speaking exclusively to Accountancy Age, Muis said reform would not be completed for half a decade and claimed EC president Romano Prodi and commissioner Neil Kinnock had grossly underestimated the difficulties.

Chris Heaton-Harris, Tory MEP and a member of the European Parliament's budgetary control committee, said: 'Kinnock's time as commissioner in charge of reform would have been better spent rooting out fraud rather than hounding out whistleblowers.'

EC will not meet 2005 deadline, says Muis

The former auditor's comments will make uncomfortable reading for the commission, and provide ammunition for Eurosceptics keen to portray the EU as a tax 'black hole' in the run up to polling day on 10 June.

While describing proposed changes as 'excellent', Muis said: 'The next commission faces a major challenge if it is to finish the reforms as currently envisaged - not least because the present executive body has not helped itself by not coming up with proper balance sheets, and there has been no discharge for nine consecutive years.'

Financial scandals have continued since the EC's mass resignation in 1998 amid allegations of widespread fraud and mismanagement.

Kinnock's spokesman, Michael Mann, took issue with comments from the former auditor. Of the 98 financial reforms set out in a white paper by the commissioner, 95 have been implemented. 'Kinnock has always seen himself as Mr Catch-Up rather than Mr Clean-Up because there was so much to be done when the code of conduct was drawn up in 1999,' said Mann.

The commission's troubles have shown no signs of letting up, with the scandal at Eurostat and a National Audit Office report suggesting fraud within the EU has doubled to £700m.