The National Union of Journalists (NUJ) has called for an international investigation into the killing of Sunday World reporter Martin O’Hagan.
Mr O'Hagan was shot dead by the Ulster Volunteer Force on September 28th, 2001, in his home town of Lurgan, Co Armagh, while in the company of his wife, Marie.
He was the only journalist killed during the Troubles though all the major paramilitaries were supposed to be on ceasefire at the time.
NUJ general secretary Michelle Stanistreet described the failure to secure a conviction of his killers as a stain on the history of policing in Northern Ireland.
She made a renewed call for the British government to establish a panel of international experts to investigate the murder and the subsequent failure of the security authorities to secure a conviction for it.
“The passage of time does not obliterate the need for an independent investigation drawn from outside the UK to investigate the murder and the subsequent police failings,” she said.
“Martin was killed because he, as a dogged, determined investigative journalist, knew too much. The widespread belief that those who murdered Martin were informers, or linked to informers and thus protected, is sadly not a far-fetched theory.
“We can best serve his memory by continuing to challenge the bullies, to ask the difficult questions and to hold those in power to account. Martin was also a solid trade unionist and we also honour him by defending the rights of workers.”
The NUJ said it planned to write to British prime minister Boris Johnson and Taoiseach Micheál Martin seeking their support for a comprehensive investigation.
In a statement, Det Supt Stephen Wright from the Police Service of Northern Ireland's legacy investigation branch said the investigation into the killing remained open, but the caseload meant they were not able to say when the review would start.
“Approaching the 20th anniversary of Martin’s murder, I am appealing to anyone who has information about who carried out this heinous act to do the right thing and tell us what they know,” Det Supt Wright said.
“We are committed to bringing to justice those responsible for Martin’s murder and will investigate any new information that is brought to us and, where credible investigative lines of enquiry are identified, we will follow them.”