Channel 4 News presenter Jon Snow has helped police with their "cash for honours" inquiries.
Police are interested in information revealed by Snow in a Channel 4 documentary about the honours system.
Snow told Press Gazette: "I made a documentary about ‘secrets of the honours system' five years ago. I also gave evidence at a Commons Select Committee in 2003. [The police] just wanted copies of both."
The inquiry began after questions arose about the way in which political parties award honours, following allegations earlier this year that Labour's leading financial backers were rewarded with nominations for peerages.
Blogger Guido Fawkes, who covered the news on his website, suggested that the police have questioned other journalists who worked on the story.
Snow was also questioned over his honours documentary when he appeared before the Public Administration Select Committee in 2003.
Speaking at the tribunal, he said: "This is about how our country is run and how it works. If we do not know how we get to this particular position, with all these appointments, and with the gongs and the rest of it, then there is a major dark place, which is not good for a democracy to enjoy."