Police must inform parents of children whose IDs were used by spies, says MP Keith Vaz said parents of those involved should be informed immediately. Photograph: Haydn West/PA The Metropolitan police has been told it would be "heartless and cruel" not to inform dozens of parents whose dead children's identities were used by undercover police officers infiltrating protest groups. Keith Vaz, chairman of the home affairs select committee, which is looking into undercover policing, said the force should immediately contact affected parents. An investigation by the Guardian has established that the identities of about 80 dead children were used by police spies working for the special demonstration squad (SDS), a unit disbanded in 2008. "It is absolutely vital that the parents of those involved should be informed immediately," Vaz said. It is heartless and cruel for this information to be kept from them. The Labour MP has written to the home secretary, Theresa May, asking how the parents will be informed. He has also asked May whether ministers were aware the practice was going on and whether it was legal. On Tuesday his committee will question Patricia Gallan, the Met's deputy assistant commissioner, who is in command of the investigation into the controversy. Gallan also leads on undercover policing for the Association of Chief Police Officers. Two undercover officers have provided detailed accounts of how they and others used the identities of dead children. One described the process as "stomping on the grave" of the four-year-boy whose identity he took and said the operation was "almost Stasi-like." The other spoke of the dilemma he felt when adopting the identity of a child who died in a road accident, but said it was justified "in the greater good." Both officers conducted research into the children's family backgrounds and were equipped with fabricated identity records such as driving licences and national insurance numbers. A third undercover police officer, whose real name is John Dines, adopted the identity of an eight-year-old boy who died of leukemia in 1968. The practice, which remained classified intelligence for several decades, has prompted widespread concern. There have also been a string of disclosures about undercover police developing intimate sexual relationships with subjects of their investigations. Of the nine undercover police identified by the Guardian over the past two years, eight are believed to have slept with people they were spying on. Yvette Cooper, the shadow home secretary, said: "We already knew that action by some undercover officers had crossed the line morally and legally, raising public concern about the way they operated and the lack of accountability. But people will find this latest news about using the identities of children who had died more shocking, and independent investigation into what happened is required. In the Commons, the Labour MP David Winnick called on May to provide parliament with answers about what he called a "gruesome practice." The Met declined to answer any questions about the controversy. Previously the force said it was investigating the matter and said the practice of using dead children's identities was not "currently" authorised. It is unclear exactly when the force stopped using the technique or precisely how many identities have been used in this way. The technique was developed by the SDS, which was founded in 1968. There is some suggestion that the use of dead children's identities was phased out in the mid-1990s. But the single complaint being investigated by the Met concerns a suspected undercover police officer deployed between 2000 and 2003. That investigation, which is being conducted by the directorate of professional standards, the complaints department headed by Gallan, concerns a family who suspect the identity of their dead son was used by a police officer who went undercover in a protest group. The family is being represented by Jules Carey, one of two solicitors representing victims of the undercover policing operations, who will also give evidence at Tuesday's hearing. The Met has been investigating his client's case for 10 days. The committee will also hold a private session to hear from a number of women who were duped into forming sexual relationships with police officers who were spying on them. The women, among 11 who are suing the Met, have been granted anonymity by the high court. Mark Kennedy, a police officer who lived among environmental activists for seven years and was exposed in 2011, will also give evidence in private.