Peers inflicted two significant defeats on the government on Wednesday evening over a bill to regulate the use of undercover informants, passing amendments to stop them participating in murder and rape, and to curtail the use of children as informants. The lords voted by 339 to 235 to ban the use of under-18s as police or MI5 informants except in exceptional circumstances, in an amendment put forward by the children’s rights campaigner and peer Beeban Kidron. Children are frequently recruited by police seeking to prosecute “county lines” gangs who coerce youngsters and other vulnerable adults into transporting illegal drugs around the UK. “In every other interaction with the criminal justice system we try to remove children from criminal activity, to take them away from harm and towards safety,” Lady Kidron told fellow peers. “But before us is legislation which formalises our ability to do the opposite.” Thirteen Conservatives also rebelled against the government, led by the former transport secretary Lord Young. He warned that if an underage informant were to be discovered and killed “the policy would be reversed the next day after a public outcry and incredulity that this was permissible”. Peers were voting on the final set of amendments to the covert human intelligence sources (Chis) bill, legislation put forward to codify existing guidance covering the handling of informants and undercover operatives used principally by the police and MI5. The government was also defeated by 299 to 284 on an amendment from the peer Doreen Massey, which proposed explicitly banning those acting undercover from being allowed to participate in a list of serious crimes, including murder, torture, rape or other sexual offences as they gained information. Ministers had ruled out introducing such a list previously, arguing that creating a list of forbidden offences could give terrorists and serious criminals ways to unmask infiltrators by asking them to engage in such banned activities. “If we create a checklist on the face of the bill we make it very easy for criminal gangs to write themselves a list of offences which amount to initiation tests,” said Lady Williams, a Home Office minister. The government also argued that because the bill would be compliant with the Human Rights Act some offences were effectively banned, meaning that it did not amount to a “licence to kill”. Campaign groups welcomed the result, arguing that it would put the UK on a par with similar western countries in setting clear limits. Dan Dolan, deputy director of Reprieve, said: “The US, Australia and Canada all recognise the need for common sense limits to prevent undercover agents being authorised to commit murder, torture or rape, and now the House of Lords has too.” The defeats by the lords mean that the amendments will return in due course to the Commons. An acceptance of the amendment calling for an explicit ban on murder and other serious crime is not thought likely, but Labour sources said that Williams had indicated that the government would look again at the question of child informants. Peers were debating the bill at the second day of its report stage. On Monday, an amendment from Shami Chakrabarti seeking to strike out immunity for undercover agents acting within authorised guidelines was defeated by 309 to 153, after the Labour leadership chose to abstain.