British Prime Minister Tony Blair was questioned on Thursday by police investigating allegations that peerages and other honors were bestowed in return for political contributions. The interview did not take place under caution, and the prime minister was questioned at 10 Downing Street for up to two hours without a lawyer present, Blair's office said. Police have been investigating claims that all three major political parties awarded seats in the House of Lords and other honors in return for secret loans. Several senior Labor Party figures have already been questioned by police, including former science minister Lord Sainsbury and Blair's Middle East envoy Lord Levy. Assistant Police Commissioner John Yates, of Scotland Yard, has said he expects to deliver a report to the Crown Prosecution Service, the body responsible for prosecuting criminal cases investigated by the police in the UK, next month. Traditionally there is no wrongdoing in lending political parties money; however, the suspicion is that the lenders were trying to buy influence. Blair has been accused of selling peerages after four businessmen, who gave Labor 4.5 million in unpublicized loans, were subsequently nominated for peerages. Labor went on to reveal it had been secretly loaned nearly 14m. ahead of the last election. The Conservative Party revealed it had borrowed 16m. from 13 wealthy backers, and the Liberal Democrats 850,000 from three backers. Lord Levy, chief fund-raiser for the Labor Party and Blair's unofficial envoy to the Middle East, was arrested in July for his alleged role. He was released on bail and has been helping police with their inquiries. He denies all wrongdoing. The developments came on the same day that the official report into the death of Princess Diana in 1997 was published. The three-year inquiry, led by former Metropolitan Police chief Lord Stevens, concluded her death was an accident and not a conspiracy. Lord Stevens rejected an allegation by Mohammed Al-Fayed, father of Dodi who died in the car accident that killed Diana and driver Henri Paul, that they were murdered by British secret agents. He said there was no murder, no conspiracy and no cover-up. He said: "Our conclusion is that, on all the evidence available at this time, there was no conspiracy to murder any of the occupants of the car. This was a tragic accident." Fayed accused the royal family, and in particular the Duke of Edinburgh, of ordering their assassination to prevent his son and Diana from marrying. The allegation was so serious that it prompted the inquiry. Lord Stevens said: "We have spoken to many of her family and closest friends and none of them have indicated to us that she was either about to or wished to get engaged." He added: "I'm satisfied that no attempt has been made to hold back information and we are confident that the allegations made are unfounded." Over 400 people, including Prince Charles, the Duke of Edinburgh and the heads of MI5 and MI6 intelligence services, were interviewed or contacted by the inquiry team. Diana's sons, her brother and her sisters endorsed the report of a police inquiry into her death. A statement from Clarence House, the office of Prince Charles, said Princes William and Harry had received a copy of the report from Lord Stevens. "They are extremely grateful to Lord Stevens and his team for the thoroughness and professionalism they have shown during their investigation, and trust that these conclusive findings will end the speculation surrounding the death of their mother Diana, Princess of Wales," the statement said. AP contributed to this report.