Undercover police operations spanning decades may have led to wrongful convictions and miscarriages of justice, the Home Secretary has warned, in the wake of ''profoundly shocking'' findings of a major review into the Stephen Lawrence murder investigation.
In a dramatic day of disclosures concerning the original police probe into Stephen's death, Theresa May announced a judge-led public inquiry is to be launched into the work of covert police and Scotland Yard's Special Demonstration Squad (SDS) - the top secret unit that was up and running for nearly 40 years.
Police moles fell under the glare of the review, which was conducted by Mark Ellison QC, after a former SDS officer Peter Francis claimed he had been deployed undercover from September 1993 and tasked to ''smear'' the Lawrence family campaign.
In his report, Mr Ellison, who successfully prosecuted Gary Dobson and David Norris for Stephen's murder in 2012, found that an SDS ''spy'' was working within the ''Lawrence family camp'' during the judicial inquiry led by Sir William Macpherson into Stephen's death in the late nineties.
Stephen's mother Baroness Doreen Lawrence fought back tears in the House of Lords as she said her family had endured ''21 years of struggle'' and there was ''still more to come'' following the most recent disclosures.
Later in the day, detectives investigating wider allegations made against undercover police and the SDS revealed three officers, including at least one of whom who is understood to still be serving, could face criminal charges over claims they slept with women they spied on.
Addressing the House of Commons, the Home Secretary said SDS officers' actions - such as failing to reveal their true identities to court or correct evidence they knew was wrong - meant there was ''real potential for miscarriages of justice''.
The Home Secretary has commissioned Mr Ellison, along with the Crown Prosecution Service and Attorney General, to conduct a further review into cases impacted by the SDS and has launched a wider public inquiry into undercover policing and the actions of the squad.
''In particular, Ellison says there is an inevitable potential for SDS officers to have been viewed by those they infiltrated as encouraging, and participating in, criminal behaviour,'' she said. ''We must therefore establish if there have been miscarriages of justice.''
Mrs May also announced that she would bring in new legislation to create a specific offence of police corruption, to replace current ''outdated'' misconduct in public office.
The QC added that he felt ''bound'' to flag concerns about the wider implications of the findings on SDS activities - namely that the way in which the unit operated could have ultimately tainted criminal proceedings.
Mr Ellison said the nature of undercover work placed serving officers inside groups of activists who came into conflict with the police and faced arrest and prosecution.
He said: ''Having a system whereby that activity was shrouded in almost total secrecy and the role of, and intelligence gained by, the undercover officer was not considered in relation to the prosecution's duty of disclosure in criminal proceedings must, in our assessment, produce the potential for there to have been unfairness in some of those proceedings.''
In Stephen's murder investigation, t he undercover officer in question - referred to as N81 - was also found to have held a meeting with acting detective inspector Richard Walton, who had been seconded to the MPS Lawrence review team, responsible for making submissions to the Macpherson inquiry.
Mr Ellison branded this meeting ''a completely improper use'' of intelligence, adding: ''We find the opening of such a channel of communication at that time to have been 'wrong-headed and inappropriate'.''
''The mere presence of an undercover Metropolitan Police officer in the wider Lawrence family camp in such circumstances is highly questionable in terms of the appearance it creates of the MPS (Metropolitan Police Service) having a spy in the family's camp,'' he said.
In addition, Mr Ellison found there is evidence to suspect one of the detectives on the original Stephen Lawrence murder investigation - detective sergeant John Davidson - acted corruptly.
Both the Independent Police Complaints Commission 2006 report into corruption allegations and the Metropolitan Police's own review in 2012 were found to be inadequate by the review.
Mr Ellison added that Scotland Yard's record-keeping on its own investigations into police corruption are a cause of concern, with key evidence the subject of mass shredding in 2003.
A hard drive containing relevant data was discovered in November 2013 after more than a year of searching for it.
Stephen Lawrence, 18, a would-be architect, was stabbed to death by a group of up to six white youths in an unprovoked racist attack as he waited at a bus stop in Eltham, south-east London, with a friend on April 22 1993.
His father Neville Lawrence said the findings were ''21 years overdue'', while Prime Minister David Cameron and Labour leader Ed Miliband expressed their shock at Mr Ellison's conclusions.
In the House of Lords, Baroness Lawrence of Clarendon said: "I believed that there was corruption at the start of Stephen's case and it's taken over a year for that, but it's taken nearly 21 years since Stephen's been killed, and the fact that we as a family had to go through all this and still there's more to come out.
"It's been 21 years of struggle and no family should have to do that."
However, in an apparent contradiction to Mr Ellison's findings, chief constable Mick Creedon, who is leading Operation Herne, the criminal investigation into allegations concerning undercover police, said investigators had found no evidence to back Mr Francis's claims of a smear campaign against the Lawrence family.
A file of evidence relating to three undercover officers had been passed to the Crown Prosecution Service for consideration, he said.
Mr Creedon also said a team had found a "tradecraft" document that was circulated in the SDS, advising that any relationships by undercover officers should be "fleeting and disastrous".