Britain and France have been savaged in a statement by the UN Committee on the Rights of the Child, which accused them of falling "seriously short" of their legal obligations in their treatment of children at Calais.

France is evacuating the last of 1,500 migrant and refugee children from the Calais Jungle, with buses ferrying them to reception centres around the country.

Since the demolition of the camp began they have been living in converted shipping containers on the site. Their applications to travel to Britain will be processed by UK officials, but Britain is resisting taking in large numbers of children.

The statement said: "The events of the past week have shown clearly that political and other considerations prevailed over the initial promises by both Governments that the situation of unaccompanied children would be their priority. The best interests of the child have been completely disregarded."

It said disagreements between Britain and France over who should take responsibility for the children had led to "major violations" of their rights. "Hundreds of children have been subjected to inhumane living conditions, left without adequate shelter, food, medical services and psychosocial support, and in some cases exposed to smugglers and traffickers."

It said neither government could claim it was caught off guard by the situation, adding: "The failures regarding the situation of children in Calais are not isolated events but highlight the shortcomings of a migration system built on policies that are neither developed nor implemented with child rights in mind."

Faith leaders have been calling on the Home Secretary, Amber Rudd, to resume the transfer of unaccompanied children to the UK. More than 200 leaders – including around 130 Baptist ministers – signed a letter printed in The Times calling for the programme to resume.

One of them, Baptist minister Juliet Kilpin, told Christian Today the children had been treated "abominably". She said they had been left behind when adults were moved off the site and that many of them had been refused the opportunity to register as children because police had taken arbitrary decisions about their age. The result was that as many as 60 had been forced to sleep in the open, with no food or shelter.

"There is no reason more planning and preparation couldn't have been done," she said. "If not, there's no reason there couldn't have been a delay in the demolition. It baffles me."

She said all of the 1,500 children should be offered asylum in Britain or France. "Vast numbers have family in the UK and they have every legal right to be here – Britain is dragging its feet in implementing their legal rights. This last week has seen serious breaches of human rights."

Kilpin was in the Calais Jungle last week and witnessed the demolition of the camp. She was critical of way the children had been left until last, saying: "To leave children as the very last people in the camp, with no community leaders, no faith leaders, with the camp on fire and looking like a war zone, is abhorrent."