Theresa May will today meet the Stephen Lawrence family amid calls for a new public inquiry into claims that police secretly hunted for information to smear their campaign.

Michael Mansfield QC, who represents the family of murdered student Stephen, said they also wanted the investigation to look at all cases of undercover activity carried out by Scotland Yard's former Special Demonstration Squad throughout the 1980s and 1990s.

It follows claims by one of the squad's former undercover officers, Peter Francis, that he was told to dig up "dirt" on the Lawrence family and their campaign for justice after Stephen's death in 1993, as well as allegations that officers secretly bugged meetings they held with the murdered teenager's friend Duwayne Brooks and his lawyers.

Mr Mansfield said Stephen's father Neville wanted to know the truth about the allegations and the now disbanded Special Demonstration Squad, which is already subject to an inquiry.

He said: "What Neville is asking for is an inquiry of the kind we had in the first place looking into not just the Lawrence case, but all these cases where this (Special Demonstration Squad) has been operating using deceit – it's institutionalised deceit.

"We're going to see the Home Secretary, and I can assure the public that that's what we're going to be asking the Home Secretary to be considering, establishing a proper, public, transparent inquiry."