ITV Meridian's Sarah Saunders reports from Warsaw.
Sussex humanitarian aid worker Sally Becker is accusing the Home Office of failing more than 100 refugees she's rescued from war zones in Ukraine.
The children, some of them orphans of the war, are desperate to travel to England, where she is hoping to organise accommodation for the entire group.
But Ms Becker - founder of British charity Save a Child - says their flight from Poland has been repeatedly blocked by Home Office 'red tape'.
Fearing they would be left in temporary accommodation indefinitely, a number of men women and children have taken the difficult decision to return to Ukraine, while others have been placed in a Warsaw refugee camp.
“I am shocked by the decision to refuse these children a safe haven” said Sally, “especially when the Government have been kept informed of the mission at every step.
"I spent three weeks in Ukraine gathering all the documentation necessary for the evacuation. Amongst the group are children who were captured and beaten by Russian soldiers and two young girls who were forced to hide in a forest when their town was occupied by Russian forces.
"There are Grandmothers who have custody of their grandchildren and were hoping to find a safe haven and the last orphaned children and their legal guardians from Dnipro.
Video shows the living conditions in one of the refugee centres in Poland.
“In light of his recent letter to the Children of Ukraine in which he states ‘we will not forget you’, I am hoping that Boris Johnson will override the Home Office decision and help me bring these vulnerable women and children to Great Britain, Sally added.
"They are not seeking asylum. Just a temporary sanctuary where they can sleep without the constant sound of sirens and the fear of being targeted by Russian missiles”.
Ms Becker helped to evacuate 54 orphaned children and their guardians from Dnipro in March, and returned to the region last month to help several large groups of children and their mothers/guardians who were desperate to leave.
Refugees are moved to another centre in Poland.
In a statement, a government spokesperson said: “It is vitally important that the best interests of children caught up in Putin’s barbaric war are protected and that they receive the right support and care.
"In many cases this will mean it is more appropriate for them to remain in the region near Ukraine where they may still have family connections, where support is available through national care systems and UN assistance, and where the language and culture may be more familiar – particularly for children with complex needs.
“The UK is proud to be a leading bilateral humanitarian donor to the crisis, and is providing targeted assistance to support the most vulnerable, including children, across the region.
“We are working with the Polish authorities to help facilitate access to the necessary care and support for these children in Poland.”