As a young college student in 1984, US-based filmmaker Shonali Bose encountered the communal riots in Delhi where thousands of Sikhs were killed by murderous mobs following the assassination of prime minister Indira Gandhi.

In the last five years she wrote a script and made a film" she calls "a demand for justice" to the victims of the riots.

"Twenty years have passed and nothing has happened," tells Bose, here to promote her film. "It's a massive shame."

The film "Amu" is also a vehement indictment of politicians who are widely rumoured to have incited the mobs.

"The people who poured oil on the flames are roaming scot-free," said Bose, whose film about the riots seen through the eyes of a teenage girl orphaned during the killing was shown in Delhi with portions where the actors talk of the involvement of government ministers silenced.

"The people responsible have high posts of power today. They have made it big and no one questions their actions. They must be punished," said Bose who lives in Los Angeles where she produces and hosts a monthly radio show about South Asia.

"If I ever had doubts that a cover up of history had taken place, they were set to rest when the censor board removed these lines of dialogue along with other politically motivated cuts and gave the film an 'A' certificate because 'Why bring up a history which is best buried and forgotten?'"

Bose said she accepted cuts because "(I) thought it an even more powerful indictment for audiences to see the widows silently moving their lips".

In the film, to be released Jan 7, Kaju, a 21-year-old Indian American girl who comes for a visit to Delhi, the home of her adopted mother.

There she (Konkona Sensharma) finds out her true identity as the child of a victim of the riots.

"The script stood out among some of the rather inane things that I was being offered in Bollywood," said Sensharma. "I liked the tale of this girl who discovers a past she did not know existed."

Also debuting in the film is Brinda Karat, a politician and Marxist ideologue. Karat is a politburo member of the Communist Party of India (Marxist), the party that supports the country's governing coalition.

She plays Sensharma's mother. The film is also being published as a book by Penguin.