London:  'Iron Lady', a film on Margaret Thatcher opened to acclaim and rancour in theatres across UK with the British Prime Minister David Cameron firing the first salvo saying the mega-movie should have been released only after her death.

Though, concedeing the portrayal of his predecessor by Meryl Streep was "a fantastic piece of acting", Cameron questioned the timing of the film, saying he wished it had been made "another day".

It is "more about ageing and elements of dementia rather than about an amazing prime minister", the British Prime Minister said.

The movie opened to full houses, but it drew fury from Thatcher's colleaguess among the Tories with a former minister Lord Hurd labelling the film "ghoulish", but its director has defended her work.

The biopic shows Thatcher as a frail sometimes confused old lady looking back at her carrier with the ghost of her late husband Denis looking on.

The film is set in the present - when the former Prime Minister is portrayed as mentally and physically frail – but contains flashbacks to her days in office.

Asked about it on BBC Radio 4's Today programme, Cameron said: "It's a fantastic piece of acting by Meryl Streep, but you can't help wondering, why do we have to have this film right now.

"It is a film much more about ageing and elements of dementia rather than about an amazing Prime Minister.

"My sense was a great piece of acting, a staggering piece of acting, but a film I wish they could have made another day."

But the movies mega-star Streep, who is tipped for an Oscar for her performance in the film has brushed aside the criticism, saying she relished the "opportunity" to play someone at the waning of her life…