More than 70 aid groups have suspended cooperation with the UN in Syria and have demanded an immediate and transparent investigation into its operations in the country because of concerns the Syrian president, Bashar al-Assad, has gained “significant and substantial” influence over the relief effort.

The coalition, which includes some of Syria’s most widely known aid organisations, told the UN it intends to withdraw from the UN’s information-sharing programme in protest at the way some of its agencies are functioning within the country.