Scotland's First Minister Jack McConnell was quizzed by police in connection with the cash-for-honours inquiry, it has been confirmed.
Mr McConnell was spoken to in London by officers from Scotland Yard last month as a witness and not under caution.
It is understood Mr McConnell was asked about the peerage nomination of former Lord Advocate Colin Boyd.
Metropolitan Police officers have been probing claims that political donations were given in exchange for peerages.
The inquiry was sparked after it emerged that a number of large secret loans had been made to the Labour Party before the 2005 general election and that some of those lenders had subsequently been nominated for peerages.
Police have so far spoken to about 90 people including Prime Minister Tony Blair and former Tory leader Michael Howard.
All deny wrongdoing and no-one has been charged.
Mr McConnell stressed he knew nothing about cash advances to the Labour Party.
When he was lord advocate, Lord Boyd was head of the prosecution service and was also the Scottish Executive's senior legal adviser.
Mr McConnell announced the peerage in April last year.
Scottish National Party MP Angus MacNeil raised the original complaint over alleged cash-for-honours to the police.
He said: "The entire Labour Party is becoming engulfed in this crisis of its own making.
"No-one believes for a second that Mr McConnell is directly implicated in securing cash for honours.
"But as a political party, Labour has financed campaigns north and south of the Border with funding from people whom Tony Blair has subsequently ennobled or knighted.
"Eighty pence in every pound donated to Labour has come from people who have received honours."
Mr McConnell was interviewed by police on 15 December, the day after Mr Blair was questioned in the cash-for-honours inquiry.
BBC Scotland's political editor Brian Taylor said the net the police had cast had now looped over Mr McConnell's head.
He told BBC Scotland's Good Morning Scotland programme: "The first minister is exasperated, he believes that he has been dragged in unnecessarily, he believes privately that there could have been an exchange of letters.
"But there is a bigger issue than embarrassment for Mr McConnell of being interviewed by the police and that is the political implication for the May election.
"The PM is at the core of this in legal terms, but he isn't facing an election and Jack McConnell is facing an election in May.
"The constant reminder of these allegations must be potentially damaging for Labour prospects at the election."