Stephen Gately died of natural causes at his Majorcan holiday home
Stephen Gately's civil partner Andrew Cowles has complained to the Press Complaints Commission over a Daily Mail article about the Boyzone star's death.
Mr Cowles claims Jan Moir's column, published in October, breached guidelines on accuracy, intrusion into grief or shock, and discrimination.
A PCC investigation will also consider the 25,000 complaints about the piece.
Ms Moir has expressed regret over her column which called the Irish star's death "strange, lonely and troubling".
The article, published on the day before his funeral, said Gately's death struck a blow to the "happy-ever-after myth of civil partnerships".
She later denied the piece had homophobic undertones.
Gately, 33, was found dead on 10 October at his Majorcan holiday home.
Post-mortem tests found he died of natural causes.
"We're now investigating this complaint which we are taking forward formally and we'll consider it together with the 25,000 complaints as soon as possible," PCC director Stephen Abell said.
Moir admitted the timing of her original Daily Mail column was "insensitive"
"We'll be writing to the newspaper with this latest complaint from Andrew Cowles."
Moir's article provoked the most complaints ever made about a single newspaper article.
Mr Abell said a full investigation was being launched now because "a connected party" had made a complaint.
The Daily Mail has yet to respond to a request for a comment.
In her column, Moir wrote: "The Gately family are - perhaps understandably - keen to register their boy's demise on the national consciousness as nothing more than a tragic accident."
But she continued: "Whatever the cause of death is, it is not, by any yardstick, a natural one. Let us be absolutely clear about this.
"All that has been established so far is that Stephen Gately was not murdered."
Writing in her column a week later, she said she regretted "any affront caused" but maintained the circumstances surrounding his death were "more than a little sleazy".
"What I meant by 'nothing natural' was that the natural duration of his life had been tragically shortened in a way that was shocking and out of the ordinary," she wrote.
"Absolutely none of this had anything to do with his sexuality," she added.
"If he had been a heterosexual member of a boy band, I would have written exactly the same article."