Concerns had been raised about passenger privacy
Children selected to walk through the full body scanners at airports must do so, the transport secretary has said.
Lord Adonis, announcing a consultation on a code of conduct for the scanners, said to exclude children risked undermining the security measures.
Civil rights groups had raised concerns that the resulting images would breach child pornography laws.
The scanners are being introduced after a failed attempt to blow up a plane in the US in December.
The government's code of practice on the scanners said airport security staff had all been vetted, including a check of criminal and security service records.
They had also been trained in aviation security and "customer service" to carry out their jobs "in a sensitive and proportionate manner."
The government said it was aware of concerns under the Protection of Children Act, but that there were also provisions for the prevention, detection or investigation of crime.
The government described its privacy controls as sufficient, but added that "some individuals, such as trans-gendered, disabled or elderly passengers, or passengers with particular religious or other beliefs might, notwithstanding the existing privacy controls, have concerns about undergoing a security scan."
It said staff would be able to handle such situations "sensitively".
Dylan Sharpe, campaign director of Big Brother Watch, said: "It beggars belief that the government is to force young children through these body scanners.
"Only last week a security guard was exposed as having abused the technology. How many more cases like that do we need before the transport secretary admits that the operators have not had sufficient training and vetting to handle this technology?
"Security minister Lord West admits that the scanners are only 50-60% effective, so why risk giving perverts and those looking to make a fast buck the opportunity to spy on us?"
The launch of the consultation comes after a Heathrow Airport security guard was given a police warning after he was allegedly caught staring at images of a female colleague in a body scanner.
The scanners, to be phased in gradually, will initially operate alongside metal detectors, and are eventually planned for use for all flights in and out of the UK.
The £80,000 full body scanners produce "naked" images of passengers.
They work by beaming electromagnetic waves on to passengers while they stand in a booth. A virtual three-dimensional image is then created from the reflected energy.
Airports around the world began introducing them after Nigerian Umar Farouk Abdulmutallab, now in custody, was accused of trying to detonate a bomb on a plane bound for the US on 25 December.