More than 150 children with close family in Britain are living alone in a Calais refugee camp, new research shows.
A report by aid charity Citizens UK found there were 157 unaccompanied children in the border camp known as the Jungle who have close family members in Britain to live with.
Four leading charities have now called for the Government to take urgent action following the report.
Citizens UK, Save the Children, Unicef UK and Help Refugees want the Government to address the number of unaccompanied refugee children in Europe, ahead of a parliamentary debate on the topic, as part of the Immigration Bill on Monday.
Of 157 children in Calais with family links to the UK, two are just ten-years-old. The charities say the children are traumatised by war, living rough and facing a long and complex bureaucratic procedure before being reunited with their families in Britain.
Immigration Minister James Brokenshire defended the Government's record, saying 24 children with family in the UK had been approved for transfer from France in the past six weeks.
Neil Jameson, of Citizens UK, said the Government needed to speed up the process for these individuals and added: "The fact that children, who have a legal right to come to the UK, are living alone in tents in Calais is a national embarrassment."
According to Help Refugees, there are currently 4,946 refugees in the camp. Co-founder Josie Naughton referred to the UK's Kindertransport scheme which rescued thousands of Jewish children from Nazi Germany.
She said: "There are hundreds of unaccompanied children in Calais and thousands across Europe, scared, alone and extremely vulnerable.
"According to Europol, 10,000 refugee children are missing in Europe. This is the same number of children that Kindertransport rescued from Nazi persecution. We hope our government remains on the right side of history."
Last year, approximately 95,000 refugee and migrant children travelled to Europe alone or lost their families in transit.
Save the Children said there were more than 2,000 lone child refugees in Greece trapped after the closure of the Balkans route. They said the Greek system was overwhelmed and safe shelters were oversubscribed.
The charity also highlighted the problem in Italy where, in a period of 48 hours last week, more than 450 children arrived alone.
Unicef suggested the EU-Turkey deal on migrants, and border closures, could be making the situation worse.
The group said it could increase the risk of abuse of unaccompanied children, psychological trauma and exploitation by traffickers and criminal gangs, amid the chaos.
The children's charity also added the new agreement could push people into taking more dangerous routes.
Lily Caprani, of Unicef UK, said: "It is simply an injustice that the life of any child, anywhere, has been put on hold for all this time - these children in Calais have families waiting for them here in the UK. They cannot be left like this, in this state of limbo."
Mr Brokenshire said: "We continue to work with the French authorities to address the situation in Calais.
"This includes improving the process for reuniting children with family in the UK where asylum claims are made in France. In the last six weeks 24 cases have been accepted for transfer to the UK."