Police handed the results of an investigation into donations to Peter Hain's Labour Party deputy leadership bid to prosecutors on Wednesday.
The Crown Prosecution Service will now decide whether to bring charges. Allegations that his campaign had breached electoral rules prompted Hain to quit as Work and Pensions Secretary in January.
It is the second dossier handed to the CPS on Labour funding in a week and means Prime Minister Gordon Brown risks being dogged by donations rows - just as his predecessor Tony Blair was during his final days in office.
Scotland Yard said in a statement it had passed the main file of evidence to the CPS on Wednesday.
"The referral was about potential breaches of the Political Parties, Elections and Referendums Act 2000 regarding donations received in connection to the 2007 Labour Party deputy leadership campaign," it said.
"We have had regular consultation with the CPS since the enquiry began and it is now a matter for the CPS to consider the evidence, advise us on whether any further enquiries are necessary and whether any charges should be brought."
The case centres on the late declaration of a 100,000 pound gift to Hain's unsuccessful campaign.
Hain has said it was an "innocent mistake" but quit to clear his name after the matter was referred by the Electoral Commission to the police.
Last week, police handed a file to the CPS on investigation into donations to Labour by wealthy property developer David Abrahams. The allegation is that he gave several hundred thousand pounds to the party but had disguised the origin by passing the money through intermediaries.
