Dental tests to determine the age of child refugees from the Calais "Jungle" camp have been backed by Labour former home secretary Jack Straw.
Calls for such procedures to be performed on children seeking to join family members in the UK provoked a political fire storm.
Mr Straw insisted he would not have ruled out the move when he ran the Home Office as he insisted that the asylum effort would be undermined if it turned out people had been lying about their age in order to gain entry to Britain.
"Officials made a judgment, we have to accept that judgment, but if there is a case for dental checks, I would certainly not as home secretary have ruled that out," he said.
"What I would say to those supporting an increase in numbers of refugees to come here is this: if it turns out those coming in here are over 18 - and the truth will emerge after a while - then it will undermine public confidence in the whole system.
"So having tests, providing they are not too intrusive and invasive, is actually a sensible thing to do for everyone concerned.
"Most of them are economic migrants and you have to be pretty firm about this.
"Part of the problem with the issue of whether they are children is you have got to test their age because you will understandably always get quite a lot of people who, knowing that it's easier to get in because they are younger, will pretend they are under 18 when they are not.
"Some of those who are at Calais are genuine refugees but an awful lot are economic migrants," Mr Straw told the Daily Mail.
The British Dental Association (BDA) said the demands for age tests were "inappropriate and unethical".
Dentists also said that such tests would not be reliable enough to determine if the refugees were children or not.
Tory MP David Davies was accused in the House of Commons of fuelling "xenophobic attacks" after he said the teenagers "don't look like children" and should be given dental checks to prove their age.
The SNP's Neil Gray also labelled Mr Davies's remarks "disgraceful".
Government handling of the process was also condemned by the head of a children's charity, who said officials had not been given adequate time to prepare for the youngsters' arrival - including organising foster homes.
Andy Elvin of the Tact fostering and adoption charity told ITV News: "It's a complete shambles - and it's a completely avoidable shambles as well.
"This is wholly the responsibility of Amber Rudd and Theresa May because the officials aren't to blame, the officials haven't been allowed to do sensible planning for these children coming over."
Across the channel in France, the sprawling migrant camp is facing demolition after a French court rejected an appeal from aid groups to delay the clearance.
The arrival of the group, made up of youngsters who are said to originate from a variety of war-torn countries - including Afghanistan, Syria and Sudan - has been so far welcomed by charities and faith leaders.
It followed a team of British officials being sent to Calais to help French authorities speed up the transfer of minors ahead of the dismantling of the camp.
The first 14 children arrived earlier this week ahead of the Jungle camp's anticipated clearance.
More children are expected to arrive soon after a team of British officials were sent to Calais to help French authorities speed up the transfer of minors ahead of the dismantling of the camp.
Campaigners including Citizens UK, which said it has reunited 60 children from Calais with relatives in Britain since March, claim to have identified hundreds of children in the camp who have a right to come to the UK - either because they have family ties here under the so-called Dublin regulations, or through the Dubs amendment.
Figures from the Home Office showed that more than two thirds of refugees who had their ages assessed were found to be adults, despite claiming to be children.