Media playback is unsupported on your device Media caption Meryl Streep: "I wanted to capture whatever it was that drew people to her or meant people have a special venom for her"

Meryl Streep has defended her portrayal of former Prime Minister Margaret Thatcher as a frail old woman suffering from dementia in The Iron Lady.

The film has drawn criticism from Baroness Thatcher's former colleagues, including former Conservative party chairman Lord Tebbit.

He called the performance "half-hysterical, over-emotional".

"I felt that if we did it in the right way, it would be OK," Streep told the BBC, ahead of its release on 6 January.

Speaking to the BBC's Arts Editor Will Gompertz, the actress, who is expected to land her 17th Oscar nomination for the film said: "There is a feeling that the walls are just more permeable between the present and the past and one intrudes on the other.

"It's something that I don't think there should be a stigma about, it's life, it's the truth.

"We've all had that moment where you can't remember why you went upstairs and so it was extrapolating that feeling of disorientation, momentary as it is," Streep added.

'Piece of art'

Told in a series of flashbacks, the film sees an elderly Baroness Thatcher struggling with advanced dementia and in regular conversation with her late husband Denis Thatcher, played by Jim Broadbent.

Media playback is unsupported on your device Media caption Michael Portillo has praised Meryl Streep's performance

The rest of the film deals with her rise and eventual fall from power, and features scenes of her bullying her cabinet into submission.

Writing in the Telegraph, Lord Tebbit said: "She could be hard - perhaps at times unfairly so - on colleagues who failed her standards.

"She was never, in my experience, the half-hysterical, overemotional, overacting woman portrayed by Meryl Streep."

It is Streep's performance as the older Baroness Thatcher which has already proved controversial.

Former Conservative politician Michael Portillo, a junior minister under the then Mrs Thatcher, praised Streep but told the BBC that he "felt uncomfortable" about the scenes of her infirmity.

"I wouldn't want to see my own mother portrayed in that way," he said. "I recognise it is a tremendous piece of art, but that will be a controversial feature of the film."

Referring Carol Thatcher's book detailing her mother's decline, Streep said: "Carol caught a lot of flak for speaking about this, but other people who have dementia in their family are grateful."