Sally Murrer, the Milton Keynes Citizen reporter who was cleared of obtaining police information illegally in a high profile court case in 2008, proposed private investigator Derek Webb as an NUJ member.
She was asked to do so after Webb, a co-defendant in the case in which the judge said he should be treated like a journalist because he was engaged in journalistic activities, was also cleared.
Murrer walked free from court after a judge ruled that prosecution evidence against her was inadmissible. She was due to face trial along with Webb and a former Thames Valley police detective sergeant, Mark Kearney, who was also cleared.
There has been growing concern within the NUJ about how Webb, who spied for the News of the World on the solicitors acting for phone hacking victims, got a union card.
Murrer told me: "I proposed Derek as an NUJ member. He was desperate for money and wanted to continue working for the News of the World.
"I'd heard the judge in our case give him journalist status which was the reason the case against him was dropped. I was consumed by the case and because of that I proposed him on the form.
"It wasn't until this all came up recently that I questioned it and wondered if more private investigators had become NUJ members. At the time I just felt sorry for him, he told me the News of the World said he had to have a press card to continue working for them.
"If I did anything wrong I am really sorry. I believe the NUJ should be for journalists and they had a chance to examine this before it was seconded and approved. I've got nothing to hide and neither should the NUJ."
Murrer was accused of three offences of aiding and abetting misconduct in a public office. Webb pleaded not guilty to five offences of aiding and abetting misconduct in a public office.
In a landmark ruling judge Richard Southwell said that any evidence gathered by police using a a bug should be excluded under European laws that protected the rights of journalists and their sources.