The United States is investigating an international aid group headed by David Miliband over allegations of corruption in projects intended to help Syrian civilians and refugees.

The International Rescue Committee (IRC) is one of three international groups to have had millions of pounds in funding withdrawn over alleged bid-rigging and bribery.

Mr Miliband, a former foreign secretary, was appointed president and chief executive of the organisation in 2013, following his exit from Westminster politics.

USAID's Office of the Inspector General confirmed on Friday that 14 entities and individuals had been suspended as part of a "complex investigation into cross-border aid programs".

This includes International Medical Corps, one of the largest providers of medical aid to Syrians, and GOAL, an Irish NGO.

Allegations relate to the organisations systematically overpaying for goods in Turkey. A senior USAID official, speaking on condition of anonymity, said private Turkish companies had sold cut-rate blankets and other basic materials at vastly inflated prices and pocketed the difference.

The items are meant to ensure the survival of hundreds of thousands of Syrian civilians, many of whom have been left with nothing but the clothes on their backs.

"What became clear in the course of this investigation was this was a pretty sophisticated operation," the USAID official said.