All police forces in the country will be made to examine their archives to search for evidence of misconduct by undercover officers following allegations surrounding the Stephen Lawrence murder inquiry.
Policing minister Damian Green admitted the probe could lead to "some very unpalatable truths" coming out, but said it was better than keeping them hidden.
He is expected to tell the chief constables of the 43 forces in England and Wales they must carry out the searches following the revelation that an undercover officer was told to find information to use to smear the Lawrence family after the teenager's racially aggravated murder in 1993.
More police forces have been asked to look at whether their officers carried out surveillance and intelligence-gathering on anti-racism campaigners surrounding an inquiry held in the fall-out of the murder of black teenager Stephen Lawrence.
The Home Office has asked West Midlands Police and Avon and Somerset Police to scour their records in respect of the Macpherson inquiry into the police handling of the Lawrence case, which held regional hearings in 1998 in cities including Birmingham and Bristol, as well as Manchester and Bradford.
Both forces have confirmed they are now carrying out their own investigations.
The investigations come after claims by a former undercover officer with the Metropolitan police that attempts were made to find information to smear the Lawrence family following Stephen's murder in Eltham, in April 1993.
"Following recent events across the country and subsequent correspondence from the Home Office, West Midlands Police are undertaking checks to see whether there is any material held that suggests intelligence or surveillance activity was ordered or carried out in respect of the Macpherson inquiry or those connected to the inquiry.We will be reporting back to the Home Office by July 10."
– Assistant chief constable Marcus Beale, West Midlands Police
"We looked into any implications from the Stephen Lawrence case a couple of weeks ago but didn't find anything.However, in light of a letter from the Home Secretary we are now carrying out a separate review to make sure we didn't miss anything.It is not the case that we are being investigated independently. We are doing our own investigation."
A retired senior Scotland Yard police officer has admitted authorising secret recordings of a meeting between a friend of murdered teenager Stephen Lawrence, his lawyers and detectives.
Police officers had wanted "an unassailable record of what transpired" in meetings in 1999 and 2000, ex-deputy assistant commissioner John Grieve said.
Mr Grieve, who was director of the racial and violent crimes task force between 1998 and 2002, told the BBC he deeply regretted any distress, dismay or alarm that his decision may have caused Brooks, or Mr Lawrence's parents Doreen and Neville.
Mr Grieve said that at the time his team were both trying to solve Stephen Lawrence's murder and lead the Metropolitan Police response to charges of institutional racism after the Stephen Lawrence Inquiry report.
He denied that officers had sought to trick or deceive anyone involved in the meetings.
Police chiefs have admitted authorising the secret recording of at least one meeting involving the friend of murdered teenager Stephen Lawrence, his lawyer said today.
Duwayne Brooks met Deputy Prime Minister Nick Clegg at his Whitehall office to discuss claims that the meetings were bugged.
It has been alleged that Mr Brooks and his lawyers were invited to meetings with police in 1999 or 2000, and that officers were given authorisation to use bugs.
Speaking outside Mr Clegg's office, Mr Brooks's lawyer Jane Deighton said evidence of the covert recording was of "immediate concern".
"We told the Deputy Prime Minister that it was untenable for any government not to do everything it could now to secure the quickest and the most thorough, and the most transparent, investigation into these allegations of police misconduct," she said.
"Duwayne was very pleased that the Deputy Prime Minister agreed that he was committed to ensuring an investigation that Duwayne himself had confidence in.
We are going to discuss and liaise with the Deputy Prime Minister's office next week about the details of that investigation.
But there was one matter of immediate concern to Duwayne and that's the allegations that he's had, that the police authorised the covert recording of his meetings with me and the police in my former offices. That is of immediate concern to Duwayne.
The deputy assistant commissioner of the police has confirmed that there are documents evidencing at least one such authorisation. We believe there are more.
We have asked the deputy assistant commissioner for the immediate disclosure of those documents.
Those documents are ones that Duwayne really wants to see and he wants to see them now, and he sees no reason why he shouldn't see them now.
Duwayne was also very pleased that the Deputy Prime Minister has agreed to raise the issue of the immediate disclosure of those documents with the Home Secretary."
A race relations worker whose evidence was key in the inquiry into the police handling of Stephen Lawrence's murder is the victim of a suspected smear campaign by Sir Norman Bettison, the former Chief Constable of West Yorkshire, it was claimed.
Mohammed Amran was recognised for efforts following the riots in Bradford in 1995, but later criticised the police during his evidence to the Macpherson Inquiry, which examined matters surrounding Mr Lawrence's death.
Mr Amran has now been notified of "alarming" evidence suggesting Sir Norman allegedly sought to discredit him and influence the way his evidence to the inquiry was received, the Independent said.
West Yorkshire Police and Crime Commissioner Mark Burns-Williamson, who notified Mr Amran and who has referred the evidence to the Independent Police Complaints Commission (IPCC), has spoken of "significant concerns" about Sir Norman's conduct when he was Assistant Chief Constable of the force.
Sir Norman is yet to respond to the allegations which the IPCC is now investigating, the Independent newspaper said.
Duwayne Brooks, who was with Stephen Lawrence on the night he was murdered by racists, will meet Deputy Prime Minister Nick Clegg tomorrow to discuss ongoing allegations of police misconduct, his solicitor said today.
It has been alleged that he and his lawyers were invited to meetings with police in 1999 or 2000, and that officers were given authorisation to use bugs.
He will attend the meeting with his legal team Jane Deighton and Beverley McBean.
If allegations that a former chief constable might have tried to alter the course of the Macpherson Inquiry are proved true, it would undermine current investigations into fears that police tried to discredit members of the family of murdered south London teenager Stephen Lawrence, a Labour MP said.
Clive Efford, MP for Eltham, where Mr Lawrence was killed in a racist attack in 1993, asked Commons leader Andrew Lansley today:
There are revelations that a report has been referred to the Independent Police Complaints Commission that a senior officer sought to gather information on someone who was about to give evidence to the inquiry with the intention of undermining that individual.
Now if that proves to be true, that seriously calls into question the way that senior officers across the country approached the Macpherson Inquiry and further undermines the police investigating the police.
Only an independent inquiry with the rights to summon people and to have them give evidence under oath will satisfy the public that this matter is truly being looked into.