Boris Johnson has been criticised by a former Archbishop of Canterbury for failing to heed a plea to help child refugees.
Rowan Williams hit out after the Prime Minister did not respond to a letter from 250 faith leaders, first published in June.
The letter accused the PM of not doing enough to extend help to child refugees, including those in Europe with links to the UK.
It added: “We call on the government to embrace that humanitarian spirit and as our Prime Minister, we urge you to act now and offer child refugees safe passage.”
Campaigners Safe Passage International say the letter, originally an open letter on its website, was sent first to Conservative HQ, then to a top government faith advisor, then to the Prime Minister himself.
However, No10 officials today insisted no letter was received, and the campaigners have not received a response.
Lord Williams said: “The absolute urgency of securing the well-being of child refugees and the possibility of allowing them to be reunited with their families is beyond dispute.
“Recent events like the fires in refugee camps in the Greek island of Moria have highlighted the vulnerability of unaccompanied children in these settings.
“It is deeply disappointing that the letter on this subject from British faith leaders to the Prime Minister has not even received a bare acknowledgment.
“We need to see effective and compassionate action from the government of this country.”
Beth Gardiner-Smith, chief executive of Safe Passage International, added: “The Prime Minister made a promise in January to protect family reunion for child refugees beyond Brexit, but so far the Government failed to deliver for these vulnerable children.
“ Boris Johnson didn’t have the courtesy to respond to the UK’s faith leaders, we urge him to respond to the growing cross party consensus that this is a moral imperative.”
The charity hit out as Tory MPs prepared to vote down a plea to maintain refugees’ rights to come to the UK after Brexit.
A Lords amendment to the Immigration Bill, which comes before MPs tonight, would put the EU’s Dublin III Regulation into UK law.
The regulation allows child and adult asylum seekers in Europe who have families in the UK to unite with them and claim asylum here.
The Lords passed the amendment earlier this month, but Home Secretary Priti Patel plans to undo it before the Bill becomes law.
Urging MPs to fight to keep the amendment tonight, Lord Williams said: “It took a government defeat in the Lords to bring the amendment back to the House of Commons.
“All Members of Parliament now have the opportunity to give vulnerable refugee children a safe and legal route to family reunion.”
Government officials argue the UK already has existing family reunion rules, which previously applied to non-EU citizens, allowing children to reunite with parents in the UK “where there are compelling reasons”.
However, officials said EU laws should not be replicated if they are “not working for us” and the focus “should remain on resettling directly from areas of conflict and instability.”
A government spokesperson said: “We have a long and proud history of providing protection to vulnerable children and this of course remains a responsibility we take extremely seriously.
“Through resettlement schemes, the UK resettles more refugees than any other country in Europe and we have granted protection to over 44,600 children since 2010 through a range of legal pathways.
“As part of our continued efforts to offer safe and legal routes to bring families together and provide support for those who need it most, we will be bringing forward reforms to fix the asylum system so that it better protects those fleeing persecution, oppression or tyranny.”