Michael Gambon in the 1986 BBC drama

The film stars Robert Downey Jr as a bed-ridden writer who relives his stories through his imagination.

But Ken Trodd, who produced the 1986 BBC TV version starring Michael Gambon, said the film was a letdown.

"There's lines in there I can't believe Dennis wrote, even on a very painful day," he told BBC Radio 4's Today.

"The natural tendency of Hollywood is to soften, and I think they've softened everything.

"There's no gallery of comic characters, the sense of the squalidness and basic awfulness of life in hospital which Michael Gambon's character struggled against."

Trodd also criticised Downey Jr's performance in the lead role, saying he "gamely" tried to reproduce Gambon's achievements, "but it doesn't really come off".

'Handicap'

Robert Downey Jr and friends in the 2003 remake

"They have the handicap that ours was seven hours and that they only have two - but they did not get the spirit of pain and balance and irony there was in Dennis' version," he said.

"This is a bit too glossy for its own good."

While the film's screenplay comes from a version written by Potter - who died in 1994 aged 59 - Trodd said it may not have been wise to have allowed him to write his own Hollywood screenplays.

"Hollywood poured money into his stuff but very rarely did these things work creatively or commercially," he said.

"He's a cultural individual, very specific to this country, his own angst and his own history.

"It may, in retrospect, have been a mistake to let him write his own screenplays for America - they're a transplant but not a convincing transplant. They rarely came off."