His ultimatum astonished and infuriated many MEPs and and raised the prospect of a second constitutional clash in a year between the European Commission and the European Parliament.
Mr Prodi's threat came as one of his nominated commissioners became the first casualty of confirmation hearings ahead of a parliamentary vote to approve them in two weeks' time. During three hours of questions, Philippe Busquin, Belgium's nominee, emerged without the support of MEPs.
But that was overshadowed by Mr Prodi's intervention, condemned by one MEP as a display of "machismo and posturing".
It was seen as a pre-emptive strike against MEPs seeking to secure a range of new powers from Mr Prodi in exchange for backing his team. The centre-right and Liberal blocs have demanded assurances that commissioners will resign if they lose support of a majority of MEPs in a vote of confidence. They also want greater access to documents and officials and more accountability from commissioners to the parliament.
Mr Prodi is increasingly angry that MEPs are using the occasion to try to extract concessions from him. On Tuesday, Hans-Gert Pottering, leader of the dominant 233-strong centre-right bloc of the parliament, said that, even if it is approved, the Commission will be on probation pending a second vote either in December or January.
Yesterday Mr Prodi said that such short-term approval would create instability and that he "could not accept such a limited mandate".
MEPs were swift in their denunciation. Mr Pottering said: "I am astonished by the reaction of Mr Prodi and his attitude to the European Parliament."
Nick Clegg, a Liberal Democrat MEP and former Commission official, said: "This is exactly the type of machismo and posturing that served Jacques Santer so badly."
But most MEPs accept that, following the mass resignation of the last Commission in March, a second crisis would deal the EU a crippling blow.
Centre-right MEPs argue that two sets of votes are necessary to approve Mr Prodi and his Commission - one covering the rest of the year, when Mr Santer's Commission was due to complete its term of office, and another covering the four years to 2004.Reuse content