Prime Minister Tony Blair was questioned on Thursday by police investigating allegations that peerages and other honors were bestowed in return for political contributions, Blair's office said.
The interview had not taken place under caution, Blair's office said. That would be the case if Blair were considered a suspect, but it is still extremely rare for a serving prime minister to be quizzed by police.
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 Labour Party figures have already been questioned by police, including former Science Minister Lord Sainsbury and Blair's Middle East envoy, Lord Levy.
Campaign funding rules allow those who offer loans — but not donations — to remain anonymous. The Labour Party has said it accepted, but did not disclose, loans of $25 million from 12 supporters. The opposition Conservative and Liberal Democrat parties have acknowledged they have also received secret loans.
Blair has been forced to acknowledge some supporters who offered the loans were later nominated for seats in the House of Lords.
Blair's office said that during the interview — which lasted more than an hour and a half — the prime minister explained why he had nominated certain individuals for peerages.
Blair, who is a barrister, was not accompanied by a lawyer.
"The prime minister explained why he nominated each of the individuals and he did so as party leader in respect of the peerages reserved for party supporters, as other party leaders do," Blair's official spokesman said, on the government's customary condition of anonymity.
Michael Howard, the former leader of the main opposition Conservative Party, said last month that he had also been interviewed by police over the "cash for honors" probe.