Humanitarian charity Unicef has welcomed a statement made by the three main political leaders over pledging their support to the UN's £4 billion Syria appeal.
Chief executive David Bull said: "Without the right supplies - clean water and warm blankets and clothes, vaccines and medicines - cold conditions could be fatal, especially for babies and young children," he said.
"Children who have suffered and witnessed so much also need psychological and emotional support and education.
"Unicef is increasingly concerned for children who are cut off from vital aid because of the ongoing conflict. Unicef will not rest until every child in need is reached."
Political party leaders have urged countries to pledge more money towards Syria, after throwing their support behind the United Nations' £4 billion appeal to help millions of Syrians forced to flee the civil war.
In a rare joint statement, David Cameron, Ed Miliband and Nick Clegg said:
More than 9 million people in Syria are suffering this Christmas, in desperate need of our help. Four million of them are children - the equivalent of every primary school pupil in England. This is an urgent humanitarian issue that transcends the differences of party politics.
Our country has a long history of helping those in dire need. As a nation, we have already given £523 million - including many generous donations from members of the public. But even more is needed to cope with the scale of the suffering.