Syrian lives are being put at risk by the failure of wealthy nations to meet promises of humanitarian aid, International Development Secretary Justine Greening warned.
Ms Greening appealed for “significant” extra help for the estimated nine million civilians affected by the fighting to be agreed at an international “pledging conference” this week.
Her alert that commitments had so far “fallen well short” came as the UK announced the allocation of the final part of the £500m it has pledged so far.
The £30m package will specifically target women and child refugees, including the provision of “safe spaces” in Syria and Iraq, food vouchers and health and sanitary funding.
United Nations secretary general Ban Ki-moon is hosting the conference in Kuwait tomorrow – a week before the scheduled start of peace talks in Geneva.
The latest UN aid appeal is its biggest ever at $6.5bn (£3.95bn) but existing pledges remain well short and undelivered despite warnings of dire consequences.
Britain is expected to offer a “significant” new sum.
More than 100,000 people have been killed so far in the battle between government forces and opponents of president Bashar Assad’s regime.
Millions more have been forced to flee their homes and the UN has highlighted concerns that many left trapped amid the hostilities now face starvation.
Baroness Amos, the UN emergency relief co-ordinator, said after visiting the capital Damascus: “The world must do more for all the people who are displaced.
“Many families are living in abandoned buildings, schools or in makeshift shelters, without enough food, clean water or medicine.
“We must help them to get through this very cold winter.”
Ms Greening said it was vital the world did not lose sight of the plight of civilians as it focused on the latest efforts to find a political solution to end nearly three years of violence.
“This is an unparalleled crisis and the world needs to respond accordingly,” she said, adding that delegates must be of a “sufficiently senior level” to pledge adequate funds.
“Governments must make sure that all the money they have already promised has been delivered and everyone should be ready to make significant pledges.
“For millions of ordinary Syrians, these pledges will mean the difference between life and death.”