Rt Hon Keith Vaz, chair of the Home Affairs Select Committee, has called for a "clear code of conduct" for police officers operating undercover.
He told ITV News that cases of undercover police officers fathering children with their subjects, or using the identities of children who have died, were "abhorrent".
"This isn't James Bond, this is happening," he added.
More top news
The Queen has arrived at Royal Manchester Children's Hospital to meet victims of the suicide bombing at the city's arena.
Greater Manchester Police have deemed a suspicious package safe after bomb disposal units were dispatched to a road in Hulme.
Across the nation a minute's silence was observed at 11am to remember the victims of the Manchester Arena terror attack.