The man behind a new blockbuster film about the Bhopal disaster that opened in India on Friday has taken out multimillion-dollar insurance against being sued.

Director Ravi Kumar is worried about facing legal action from Dow, the US chemical company that took over Union Carbide, which managed the pesticide plant that leaked 30 years ago and killed 25,000 people in Bhopal.

His film, Bhopal: A Prayer for Rain, starring West Wing actor Martin Sheen, pins the blame for the accident on Union Carbide. It ends by pointing out that the company has never apologised.

Kumar did not disclose the value of the libel insurance, though he said it was significant. "Producers of the film are taking no chances," he said. "We feel pressure from a lot of groups."

Sheen plays the Union Carbide chairman of 1984, Warren Anderson, one of the most hated men in India. A fugitive from Indian justice for decades, Anderson died in Florida on September 28.

In the film, Anderson says the firm had "plausible deniability" over the disaster. Sheen himself has lent support to the campaign for justice for the thousands of survivors who are still suffering.

The film also stars well-known Indian actors including Kal Penn and Rajpal Yadav. It opened in India on December 5, but has not yet been released in the UK.

The premiere in Bhopal left some of the survivors and activists in the audience in tears. It graphically shows the agonising suffering of people exposed to the leaking gas, and a hospital being completely overwhelmed.

The film follows a poor rickshaw driver, Dilip, as he proudly lands a job at the Union Carbide factory. He soon discovers that managers are ignoring safety standards, but keeps quiet about it so as not to lose his job. He then talks to a journalist, but it is too late to prevent what Indian newspapers have branded the "Bhopal holocaust" from unfolding.