Danny Boyle has given his strongest indication yet that a sequel to his cult film about Edinburgh drug addicts, Trainspotting, may yet find its way to the big screen.

Speaking to cinematical.com, Boyle said a follow-up to his 1996 movie, which starred Ewan McGregor, Robert Carlyle and Jonny Lee Miller, "will happen", though he declined to set out a timeline. The sequel would be based loosely on Trainspotting author Irvine Welsh's novel Porno, though Boyle said he did not consider the book to be as good as its predecessor.

"It will happen, I think," said Boyle. "I mean, we'll approach them all again about it, but it will depend on what place they're all at.

"We have a very strong idea that it would be a wonderful thing to do again when they have aged clearly into a mid-life crisis. They're not quite there yet, I don't think."

Boyle added: "The book Porno is not a great book in the way that the original novel is genuinely a masterpiece. But we have been doing some work on it, and it's got potential. And when the moment's right, I think we will approach it."

The Oscar-winning film-maker said the original cast did not look old enough to play ageing versions of Rent Boy, Sick Boy and Begbie, despite Welsh's novel being set only a decade after Trainspotting. Porno sees the characters, along with the hapless Spud, becoming embroiled in a scheme to raise cash by making a pornographic movie.

One of the major obstacles to a full cast reunion is McGregor, who fell out with Boyle after the director replaced him with Leonardo DiCaprio in 2000's The Beach. "Danny and I don't speak, we haven't spoken for years," McGregor said last year. "There was a falling out of sorts over The Beach and that was quite a messy and hurtful time."