UK PoolCommons Speaker Sir Lindsay Hoyle has said he passed on information on Lord Mandelson to the police, appearing to confirm reports he told the Metropolitan Police the peer was a flight risk.
It comes after lawyers for the peer complained about the force's decision to take him into custody on Monday, as part of its probe into misconduct in public office allegations.
Sir Lindsay told MPs he had passed on "relevant" information about the peer in "good faith" and it was "regrettable" it had ended up in the media.
Lord Mandelson's lawyers say he had agreed to an interview next month, and the decision to arrest him was prompted by a "baseless" suggestion he was planning to move abroad.
Making a statement in the Commons, Sir Lindsay said he felt it was his "duty and responsibility" to pass the information he had received to police.
He did not provide any details, but the BBC understands he passed on information he received in the British Virgin Islands during a visit last week that Lord Mandelson was planning to travel there.
Lord Mandelson was arrested on Monday afternoon and taken to Wandsworth police station in London for interview.
He was at the police station for nine hours before being released on bail in the early hours of Tuesday morning.
It is also understood Lord Mandelson surrendered his passport as one of his bail conditions.
It comes after the force launched an investigation earlier this month over allegations that, while he was serving as a minister, Lord Mandelson had passed on market-sensitive government information to the late convicted paedophile Jeffrey Epstein.
The BBC understands that Lord Mandelson's position is he has not acted in any way criminally and that he was not motivated by financial gain. Lawyers for the peer say he intends to co-operate with police to "clear his name".
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