"Germany, the Netherlands, Sweden and the UK continue to give generously while major donors Qatar, Saudi Arabia, and the US have contributed a smaller percentage of their fair share," the anti-poverty charity Oxfam said.
The humanitarian organization accused better-off countries of not offering enough aid funding and resettlement places to Syrians.
"In comparison Syria's small neighbours, Lebanon and Jordan — which host nearly 2 million refugees — have spent the equivalent of 6,892% and 5,628% of their fair share in aid respectively," said Andy Baker, head of Oxfam's Syria crisis response.
In 2015, just over half the funds needed to help people in Syria and surrounding countries were donated, the group emphasized.
London is hosting a Syria Donors Conference 2016 this week that will bring together world leaders, international organizations and charities in an attempt to draw attention to the plight of the Syrian people.