The politician told The Telegraph he denied the claims, which relate to alleged abuse at a children’s home, and would sue the Corporation if they were aired.
By Steven Swinford and Sam Marsden
The show, broadcast on Friday night, did not name the politician.
The investigation comes after the BBC was accused of covering up a previous Newsnight investigation into allegations that Jimmy Savile abused children.
Journalists at the flagship current affairs programme accused the BBC of pulling their report last December because the Corporation had planned Christmas tribute shows about the late presenter and DJ.
Details of Newsnight’s latest probe leaked out at 10am on Friday morning after a Tweet by Iain Overton, editor of the London-based Bureau of Investigative Journalism, which had been working on the story for the BBC.
“If all goes well we’ve got a Newsnight out tonight about a very senior political figure who is a paedophile,” he wrote.
Rob Wilson, the Conservative MP for Reading East, said Newsnight’s handling of the highly sensitive allegations about a senior politician raised fresh questions about the BBC’s management…