The Edinburgh author teased that Spud, Begbie, Sick Boy and Renton may return in a third Trainspotting film.
The 1996 original quickly became a cult classic and turned Ewan McGregor and Robert Carlyle into household names. It was followed two decades years later by T2 Trainspotting which reunited the cast and director Danny Boyle.
Speaking on the Anything Goes podcast with James English, he admits: “You think the Godfather III, Terminator III - there’s the temptation to do the Holy Trinity, it might evoke Danny’s inner Catholic.
“It took us long enough to work up the bottle to do number two.
“They’ll all be in the rest home by the time we had the bottle to do number three.
"We’d have to get moving on it pretty quickly.
“But it’s something that would be massively interesting to me.”
Welsh also admitted he wants to make a Begbie spin-off.
He added: "The one I would like to do is a Begbie stand-alone. Just a short 90-minute film of Robert Carlyle going nuts.”