Detectives investigating the "cash for honours" affair yesterday handed over their main evidence file to the Crown Prosecution Service.
Prosecutors will now assess information gathered in a 13-month inquiry by the police team led by Assistant Commissioner John Yates before deciding whether charges should be brought.
The Metropolitan Police said the 216-page document was handed over together with supporting material. It was the 12th submission made to the CPS by the inquiry team.
The Met said in a statement: "It is now a matter for the CPS to consider the evidence, advise us on whether any further inquiries are necessary and whether any charges should be brought." Altogether 136 people - including Prime Minister Tony Blair - have been questioned in the course of the investigation, either as witnesses or suspects, and 6,300 documents passed to prosecutors.
Three people remain on police bail - Mr Blair's chief fundraiser Lord Levy, No 10 aide Ruth Turner, and wealthy Labour Party backer Sir Christopher Evan. Lord Levy, Ms Turner and Sir Christopher - who all deny any wrongdoing - were arrested in the course of the 13-month inquiry in connection with alleged offences under the Honours (Prevention of Abuses) Act 1925.
Lord Levy and Ms Turner have also been questioned in relation to allegations concerning conspiracy to pervert the course of justice. The police investigation was launched in March last year following a complaint by Scottish National Party MP Angus MacNeil. It followed the disclosure that the House of Lords Appointments Commission had blocked the award of peerages to four wealthy Labour backers who gave undisclosed loans to the party in the run-up to the 2005 general election.
The inquiry was subsequently widened to cover loans made to the Conservative Party.
The CPS confirmed in a statement it had received the file and said it would now consider whether to bring any charges.
"It will now be reviewed in accordance with the Code for Crown Prosecutors to determine whether any individuals should be charged with any offences," the statement said.
"These decisions will be notified to the MPS (Metropolitan Police Service) in due course and will be publicly announced after concerned parties are notified."
The decision on whether to bring any charges will be made by Carmen Dowd, head of the special crime division at the CPS. The director of public prosecutions, Sir Ken Macdonald, said he will stand back from any decision as he was for three years a member of Matrix Chambers, where Mr Blair's wife, Cherie, also practises.