Chief constable wants broadcaster to hand over material about revelations that undercover officers spied on Lawrence family

A top police officer is trying to force Channel 4 to hand over documents about the whistleblower who revealed that undercover officers had spied on relatives of Stephen Lawrence and their supporters.

Mick Creedon, the chief constable of Derbyshire, who is heading a team investigating the alleged misconduct of the secret undercover unit, has demanded the broadcaster provide documents and unshown footage about disclosures by the former undercover officer Peter Francis.

The police say that they need the material as they are investigating whether a breach of the Official Secrets Act and other offences have taken place – months after the high-profile claims by Francis were aired on Channel 4's Dispatches and published in the Guardian. The police say they are concerned he may have compromised other undercover spies and put the safety of their families at risk.

Last week, lawyers for Creedon confirmed they intended to pursue a court order to compel Channel 4 to hand over "all written and electronic correspondence with Mr Francis together with any notes and all unedited video footage", reinforcing a demand made in a letter sent in October.

Francis has been a key source in recent years behind a series of revelations about the covert unit that sent long-term spies to infiltrate and disrupt political groups for 40 years.

He told the Guardian: "The threat of prosecution is designed not only to keep me quiet but also all the other hundred or so former undercover officers from ever speaking out. It saddens me but does not surprise me that the police don't like their dirty undercover secret being revealed to the public. They should investigate the allegations properly."

His disclosures have come under investigation by a team of police officers, led by the chief constable, that was set up to examine a broad range of alleged wrongdoing by the undercover Scotland Yard unit.

The team, headed by Creedon at the request of the Metropolitan police, has demanded that Channel 4 hand over documents and footage about "a large amount of information" they believe has been disclosed by Francis, including:

• He and other undercover officers were asked to find information to undermine the campaign by the family and supporters of Stephen Lawrence, the teenager murdered by a racist gang, to bring his killers to justice.

• The undercover spies routinely formed sexual relationships with the campaigners they had been sent to spy on.

• A safe house that the undercover unit stopped using years ago.

The legal demand has emerged after the police team had told Francis at one point that they were treating him as a "witness" to their investigation, and hoped he was "prepared to assist the inquiry". The team has yet to arrest anyone since it was set up in 2011, nor has anyone been prosecuted.

Channel 4 intends to resist the demand by Creedon's lawyers. Guardian reporters collaborated with Channel 4 to produce the Dispatches programme last June.

Over the past four years, Francis has detailed how his superiors in the covert unit, the Special Demonstration Squad, instructed him to infiltrate anti-racist campaigns between 1993 and 1997. He has also shed light, for example, on how the spies used their fake cover names in court cases and stole the identities of dead children. These are among the allegations under investigation by Creedon's team.

Sir Bernard Hogan-Howe, the Metropolitan police commissioner, has apologised for the "shock and offence" the theft of the dead children's identities caused.

Francis's claims forced the police to admit publicly that Scotland Yard had used undercover officers to collect information on groups who were campaigning for a proper investigation into the Lawrence murder.

In October, lawyers for Creedon sent a letter to Channel 4, saying: "In the Dispatches episode The Police's Dirty Secret, an individual by the name of Peter Francis is believed to have provided a large amount of information to the production team.

"It is of concern to the senior investigating officer, Chief Constable Mick Creedon, that Mr Francis may have revealed the names of fellow operatives, both past and present. In many cases, just the revelation of their true/pseudonym identities could put their lives and well-being of their families at risk.

"Similarly, in the broadcast, Peter Francis revealed a meeting location for SDS colleagues. It is of grave concern that he may have revealed further covert police premises and methodology practised during his deployment with the unit."

The SDS, which was disbanded in 2008, stopped using the meeting place in Balcombe Street, central London more than a decade ago.

Creedon's lawyers cited Francis's disclosures about "the acceptance of sexual relationships between officers and activists as well as the smearing of high-profile campaigns". They said his team was investigating "possible offences of breaches of the Official Secrets Act, misconduct in a public office, perverting the course of justice, and allegations of sexual offences".

Last August, Francis offered to speak to Creedon's inquiry, known as Operation Herne, if police chiefs withdrew their threat to investigate him over the Official Secrets Act.

He has said that on several occasions since he left the Metropolitan police in 2001, the force has threatened to prosecute him under the act if he revealed anything about his former unit.

After Creedon's team said they could not give him immunity from an Official Secrets Act prosecution, Francis said he was not happy to speak to their inquiry.

However, Francis is due to give evidence this week to an associated official inquiry that has been asked by the home secretary, Theresa May, to examine the undercover infiltration of the Stephen Lawrence campaign and other allegations.

He is doing so as Mark Ellison, the barrister heading this inquiry, secured from the attorney-general, Dominic Grieve, limited immunity to enable him to speak to his inquiry.

Derbyshire police said they did not want to comment. Since 2011, Francis has been calling for a public inquiry into all the allegations surrounding the undercover infiltration of political groups.