The father of murdered teenager Stephen Lawrence said he felt "betrayed" after allegations emerged that undercover police officers were told to spy on his family in the hope of finding information to smear them.
Neville Lawrence told ITV News he wanted a judge-led inquiry into the claims and dismissed the inquiries announced by the Home Secretary, calling them "completely unsatisfactory".
Theresa May said she would extend two ongoing inquiries into alleged police wrongdoing to cover the allegations made by former undercover officer Peter Francis.
ITV News UK Editor Lucy Manning reports:
Mr Lawrence added that the allegations had "taken away the faith" he had in the police.
Metropolitan Police commissioner Sir Bernard Hogan-Howe said if the smear plot allegations turned out to be true it would be a "disgrace" and the force would apologise to the family.
Sir Bernard added that although he understood Mr Lawrence's concerns over the alleged smear plot, he hoped to "reassure" the murdered teenager's father that the inquiries would be objective.
Mr Francis told Channel 4's Dispatches that while infiltrating an anti-racist group in the 1990s, he was put under "huge and constant pressure" from superiors to "hunt for disinformation" to undermine those demanding a better investigation into Lawrence's murder.
The former undercover officer said he was told to withhold information about his activities from the Macpherson Inquiry into the Met's handling of the murder investigation.
He was also apparently told to dig up "dirt" on Neville and Doreen Lawrence shortly after 18-year-old architecture student Stephen was killed in an unprovoked racist attack at a bus stop in south-east London in April 1993.
Prime Minister David Cameron said the allegations were "horrific" and he vowed to "get the full truth out".
Mrs May told MPs in the House of Commons that the allegations will be considered by an inquiry being led by Derbyshire chief constable Mick Creedon under the oversight of the Independent Police Complaints Commission, as well as the review of alleged police corruption in the original Lawrence inquiry being conducted by Mark Ellison QC.