The makers of an acclaimed documentary about the Tiananmen Square demonstrations say that a lawsuit brought against them by one of the leading student activists shows that she has abandoned the principle of freedom of speech.

Chai Ling, once among the most-wanted people in China, is suing the makers of Gate of Heavenly Peace, claiming that a website accompanying the film infringes the trademark of her US-based software firm, Jenzabar Inc. The company claims that Long Bow Group, a small independent organisation based in Boston, is “motivated by ill-will, their sympathy for officials in the Communist Government of China, and a desire to discredit Chai, a former student leader in the pro-democracy movement”.

A court has already dismissed a defamation suit brought by Ms Chai. The claim that the film-makers are infringing trademark by mentioning Jenzabar on their website also looks unlikely to succeed, according to court statements.

But the case has led to accusations that Ms Chai has forgotten the ideals of freedom of speech. Carma Hinton, a founder of Long Bow, told The Times that the former activist appeared to have set aside the ideals of an open society for which she fought so courageously 20 years ago on Tiananmen Square.

“It is sad that it has come at this moment, on the eve of the 20th anniversary,” she said. Long Bow says that Jenzabar dismissed an offer to settle out of court last month.

The film includes a controversial interview with Ms Chai a week before the protests were crushed in which she says that only through bloodshed can the students fulfil their aims. Speaking between tears, she tells her interviewer: “The students kept asking, ‘What should we do next? What can we accomplish?’ I feel so sad, because how can I tell them that what we are actually hoping for is bloodshed, for the moment when the Government has no choice but to brazenly butcher us?

“Only when the square is awash with blood will the people of China open their eyes. Only then will they really be united. But how can I explain this to my fellow students?”

The lawsuit against Long Bow makes no mention of this interview.

Since its release in 1995 the film has drawn the anger of both the Chinese authorities and several student leaders and has become a significant source of material on the movement.

However, the makers now fear that the aim of Ms Chai is to put Long Bow, a non-profit organisation, out of business by bankrupting them through legal costs.

Their appeal says: “We believe that in commemorating the events of 1989 20 years on, it is important to reflect also on the value of independent thought, unfettered historical research, the collection and protection of archival materials and the freedom of speech in our own environment.”

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