The former manager of Thin Lizzy has accused An Post of "steamrolling" ahead with 50th anniversary stamps in the band's honour despite "it being a year too early".
Terry O'Neill told the Herald he had contacted An Post to say 2019 did not mark the 50th anniversary and "that would not take place until next year".
"They went ahead any- way," he said. "They could have changed the dates. It was a simple enough thing to do.
"Instead, they behaved like Boris Johnson or Donald Trump and steamrolled ahead without trying to rectify this. I have credibility on this.
"Most musicians throw their diaries away, but I was there and I know when Thin Lizzy started out and it was January 1970, not October 1969.
"I'm sure Phil would've been annoyed, as he liked to get things right, he was such a perfectionist.
"He always wanted to do the right thing, and this isn't just some musicians going on tour marking the wrong date. This is stamps and that's a historic thing.
"It's a matter of public record and it's the wrong date."
An Post issued a statement, that read: "No confusion here. We are marking 50 years of Thin Lizzy - from the time in late 1969 when they talked about playing together, right through their decades of successful albums and tours, right up to the present day when they are still giants of Irish rock."
An Post released the two new stamps in Dublin yesterday at a ceremony attended by Lynott's daughters Sarah and Cathleen, his grandchildren and his ex-wife, Caroline.
An Post said fans queued at the GPO on O'Connell Street to be the first to snap up the booklets of stamps.
One features a portrait of Lynott by artist Jim Fitzpatrick while the other is of the album artwork from Black Rose, released in 1979.
The Dublin band rose to international fame with hits such as The Boys Are Back In Town and Whiskey In The Jar.
Lynott's mother, Philomena, who had long kept her son's legacy alive, died in June at the age of 88.
She was the author of My Boy, a best-selling memoir in which she told Lynott's story from his upbringing in Manchester and Dublin to his success on a global scale as a charismatic rock star.
The €1 stamps are available at post offices across Ireland and online at irishstamps.ie.