The Ritzy cinema in Brixton, south London, has cancelled a one-week run of Injustice, the documentary accusing eight serving police officers of killing black people in custody.

The cinema, owned by the reggae tycoon Chris Blackwell's Island group, said yesterday that on legal advice it could not risk jeopardising its commercial future. Attempted screenings elsewhere have brought the threat of legal action.

The film's makers, Migrant Media, described the decision as "cowardly and unbelievable". They fear it could undermine plans to distribute the film nationally and are preparing to sue for breach of contract.

"The families [of those who died] are really upset and angry," said Ken Fero, the director. "This really is insult added to injury for them. If this film cannot be shown in the heart of Brixton, where can it be shown? This film has been previewed in cinemas like the Curzon [in central London] brave enough to show it. It does not look very good for the Ritzy that it collapsed without the police even sending a solicitors' letter."

A spokeswoman for the Ritzy, which prides itself on being a cultural hub of black Britain, confirmed that it had not had a specific warning. "We made a business decision on advice from our lawyers. We cannot risk everything for the sake of one film. We know people are not going to be happy about it, but we had to act on the advice."

The film tells the story of the deaths in custody of Joy Gardner, Brian Douglas and Shiji Lapite, among others, and was made together with their families over six years. Lawyers for the officers concerned and the Police Federation have warned of a defamation action against those who show it.

In a statement, the federation said none of those named as "murderers" had been found guilty of anything. They had not been consulted before filming, and had repeatedly been refused an advance view of the completed film to respond to allegations.