The UK will provide £21 million for refugees from Syria's bloody civil war.
The conflict between Bashar al-Assad's loyalists and anti-government fighters has claimed 60,000 lives and displaced an estimated 670,000 since it began in March 2011.
International Development Secretary Justine Greening announced the gift at the Za'atri refugee camp, in neighbouring Jordan. An estimated 65,000 refugees are registered at the camp, with 30,000 arriving this year alone.
Half of the new money will go towards the humanitarian effort in Jordan, whose government claims it currently harbours more than 300,000 Syrian refugees.
The rest of the money will go to aid agencies to restock medical facilities and treat tens of thousands of injured and sick people inside Syria. It will also be used to buy vital supplies of bread and flour and winter clothing.
Syrian refugees' plight has worsened recently with severe winter conditions adding to food shortages caused by heavy rain followed by a drop in temperatures.
Ms Greening said: "My visit today has given me the chance to see first-hand the incredible generosity of spirit that ordinary Jordanians have shown in opening their homes to complete strangers in need.
"It is a story repeated in towns and villages in Syria's neighbours across the region, and I salute these ongoing efforts from governments and host communities alike.
"But we cannot and must not leave them to shoulder this response alone.
"This is a man-made crisis. That man is Assad."
The new tranche takes the UK's contribution to humanitarian aid for Syria to £89.5 million since fighting began, dwarfing Russia's £5m, China's £4m, and France's £10.8m.
Ahead of a Syria donor conference in Kuwait on January 30, Ms Greening urged other delegates to give more aid to help with the crisis.
She said: "The UK and a handful of others have consistently led the way in responding to this crisis.
"But while a small number are doing a lot, the vast majority are still not doing enough.
"This is simply not acceptable and it has to change."
David Cameron visited the Za'atri camp in November and vowed to work with US president Barack Obama to find ways to end the bloodshed in Syria after hearing "horrendous" stories of suffering from refugees.
The Prime Minister said: "I wanted to hear for myself the stories of people who have been bombed and shot and blasted out of their homes in Syria by a deeply-illegitimate and unpleasant regime that is raining down death and destruction on its own people."