An international advocacy group has accused the United Nations of not being neutral in the Syrian conflict, claiming the world body is prioritizing its relationship with the Damascus government over delivering aid to civilians.

The Beirut-based Syria Campaign says in a report released on Wednesday that the U.N. "allowed the Syrian government to direct aid from Damascus almost exclusively into its territories," at the expense of establishing regular aid access to hundreds of thousands of Syrians besieged by government forces.

The Syria Campaign lobbies governments and international organizations to improve access in war-torn Syria. Its report quotes U.N. employees and former officials, and draws on public U.N. reports and other news reports and analyses.

The report claims the United Nations is "in serious breach of humanitarian principles."