A senior war crimes prosecutor has announced she is resigning from a United Nations panel on Syria, saying she has lost faith it will ever bring criminals to account and that “everyone is bad” now in the war-torn country.

Carla Del Ponte said she was quitting the three-member commission investigating human rights abuses in Syria after five years because it "does absolutely nothing".

"We have had absolutely no success," she said on Sunday. "For five years we've been running up against walls."

Mrs Del Ponte, who has previously sat on tribunals that investigated atrocities in Rwanda and Yugoslavia, has repeatedly decried the UN Security Council's refusal to appoint a similar court for Syria's six-year-old civil war.