The BBC say their Panorama team has been threatened after airing a programme investigating Daniel Kinahan’s role in boxing.
‘Boxing and the Mob’ aired on the channel on Monday and looked into the suspected crime boss’s influence in the sport.
Police in Northern Ireland have now warned about an “unspecified threat” from “unnamed criminal elements in relation to the programme”.
Jo Carr, the BBC's head of current affairs, said: "The BBC places the utmost priority on the safety of our teams, whose journalism plays a vital role in a free society. It is despicable and intolerable if thugs think they can muzzle a free press through intimidation
"We will continue to throw light into even the murkiest of corners.”
Kinahan has been publicly lauded by fighters such as Tyson Fury and Billy Joe Saunders in the past, who are amongst more than 250 fighters signed to management company MTK Global.
Lawyers for MTK Global told the BBC: ”It is true that Mr Kinahan provides some personal advice to a number of boxers managed by MTK Global and we are instructed that Mr Kinahan also provides such advisory services to boxers who are managed by other worldwide boxing management companies too.”
They also said Kinahan had never owned, controlled or been an employee of MTK Global.
Kinahan, who has no criminal convictions, has been named in the Irish courts as head of one of Europe’s most prominent drug cartels.
He has been linked to involvement in drug trafficking and execution-style murders by the courts in Ireland, as well as suspected involvement in a feud with a rival Dublin gang that has led to the murders of 18 people.
Kinahan’s lawyers responded to “wild” and “false” allegations against him and told the BBC: "In so far as our client's record in boxing is concerned, he is proud of his record in boxing to date.”
“He has operated on the basis of honesty and with a commitment to putting fighters’ needs first. Mr Kinahan is a successful and independent adviser in the boxing industry.”
There have been calls for tighter regulation of the sport but Robert Smith, the general secretary for the British Boxing Board of Control, has conceded there is nothing the governing body can do to prevent his involvement.
“It was disappointing for the sport, obviously,” Smith told The Guardian. “But the gentleman is not licensed by the British Boxing Board in any capacity.
“We don’t license MTK as a promoter. We license individuals so the named promoter is Lee Eaton [who works for MTK] and he is the only person we deal with.
“The programme hasn’t done the sport any good but we’ll move on and take any steps that are necessary. But I think it’s down to the authorities in Ireland to deal with the matter.”