The head of the Metropolitan Police Authority yesterday told the organisation to "grow up" after they made legal threats over the screening of a documentary about deaths in police custody.

Lawyers representing at least 13 serving officers some of whom are described in the film by bereaved family members as "killers" and "murderers" have attempted to stop the documentary being shown. Despite the threats, the Metropolitan Police Authority yesterday organised a viewing of the 98-minute film, Injustice at a venue in central London to an invited audience of journalists and campaigners. Lord Toby Harris the head of the MPA reacted angrily to the action by the Police Federation, the Association that represents junior ranks. He said: "The Police Federation have got to grow up. There are serious issues at stake, we want to see what is on the film and to see whether there are issues that need to be examined further.''

Solicitors representing the Police Federation have written to cinemas and venues planning to show the documentary warning them they could be sued if the film contained "defamatory material".

The powerful documentary by two campaigning directors highlights the experiences of some relatives of those who have died in police custody. Victims include Roger Sylvester who died after being restrained by police at his home in north London in 1999, Joy Gardner who died six years earlier, also in north London, after police and immigration officers stuck 13ft of tape around her face while trying to restrain her, and Shiji Lapite, a 34-year-old Nigerian who died in a struggle with police again in North London in 1994. An inquest jury returned a verdict of unlawful killing.

Brian Douglas died from brain damage when struck by a baton after being stopped for bad driving in 1966. Ibrahima Sey, 29, died at a police station in east London in 1996 after being sprayed in the face with CS. And Harry Stanley, 46, was shot dead by police in a street in East London while carrying a table leg after wrongly being identified by 999 caller as a suspected IRA terrorist. Peter Herbert from the Society of Black Lawyers called for the Government to hold a public enquiry into all the deaths in custody in the past 20 years.