"If you don't start treating the senior pros around here with a little respect," he told him, "you're out the door and I'll see that you never get another club."
Jack Charlton - for it was he - has always believed in the direct approach. But as he recalled that moment yesterday, while launching his book at the Cafe Royal, his face clouded.
The news of Gascoigne's latest troubles, and his reported assault on his wife, is proving difficult for Charlton to reconcile with the way he recalls Gascoigne in his book - "Gazza was never a nasty or vindictive lad, and he isn't to this day."
He said he had been "very upset" to hear about the alleged domestic incident. "I am very disappointed in Paul," he said. "The other things about him I could understand but there are some things you don't do."
So would he have dropped Gascoigne from his team if he had still been in charge of him?
"No," Charlton replied, with an honesty that jolted like one of his tackles for Leeds United. "You don't cut off your nose to spite your face."
Standing in front of a microphone with his feet slightly apart, he resembled a boxer. But it was affection, rather than blows, which rained down on him as he traversed the familiar landscape of his life.
That "little black book" of players to get even with - only metaphorical, ref - which got him into so much trouble all those years ago. Who was in it, then?
He demurred. "I wouldn't want to embarrass anyone now. Apart from Johnny Morrissey."
What about the time he was invited to apply for the England job in 1977 and never even got a reply to his letter?
"That was the only time I've ever applied for a job in my life," he said. "It was a bit strange. I always felt that I had the right sort of pedigree for the job. I'd always been an FA guy, I'd done their coaching course. I might have done the job better than Don Revie, or I might not have. But I would like to have been given the opportunity."
As an Ashington lad, he is naturally delighted at the way Newcastle - the club he managed for a year before resigning in 1985- are playing at the moment. "They are still the only team in the country where if they score I stand up automatically."
Black and white stripes were surely not far from his mind when he expanded on one of the few regrets in his life - "there are football clubs I think I might have spent a little more time at."
His other, deeper regret was his poor relationship with his younger brother, whom he criticises in his book for distancing himself from his family and not visiting their mother, Cissy, before she died.
"It was very difficult writing about Bobby," he said. "I didn't want to do it in the first place, but the people I did the book with felt it was very important. It was as short as I could get away with."
There has been no reaction so far from "Our Robert". "I have no idea if there will be any reconciliation. We will find out in the future. I don't think he'll be too happy with what I've done."
For a man who has spent the last 35 years of his life in football, Charlton, 61, seemed remarkably buoyant since resigning as the Republic of Ireland manager in January. "I haven't missed it one little bit," he said. "If I'll get back to football, I don't know. It's difficult when you have been working in what is virtually part-time conditions for 10 years. To suddenly go back to seven-days-a-week football is something I would find very hard.
"I've got many other interests in my life now. I've got nothing more to achieve, really... maybe to catch the biggest salmon in the country or something like that..."
At which point Jack Charlton, OBE, Freeman of Dublin, gave a sly grin. It's hard to believe he won't be back somewhere.
l Jack Charlton - The Autobiography with Peter Byrne (Partridge Press, pounds 16.99).Reuse content