Renowned former war crimes prosecutor Carla Del Ponte is resigning from the UN's Syria panel, saying in five years it has had no success at all.
Talking to the Swiss magazine Blick, she expressed frustration about the independent Commission of Inquiry on Syria and criticised President Bashar Assad's government, the Syrian opposition and the international community.
"We have had absolutely no success," she told Blick on the sidelines of the Locarno film festival on Sunday. "For five years we've been running up against walls."
Ms Del Ponte gained fame as the prosecutor for the international war crimes tribunals that investigated atrocities in Rwanda and Yugoslavia.
She has repeatedly decried the Security Council's refusal to appoint a similar court for Syria's civil war that is estimated to have left at least 400,000 dead.
Permanent member Russia, which can veto council actions, is a key backer of Assad's government.
"I give up. The states in the Security Council don't want justice," Ms Del Ponte said.
"I can't any longer be part of this commission which simply doesn't do anything."
Appointed in September 2012, Ms Del Ponte was quoted by Blick as saying she now thinks she was put into the role "as an alibi".
"I've written my letter of resignation already and will post it in the coming days," she said.
In her comments to Blick, Ms Del Ponte described Syria as a land without a future.
"Believe me, the terrible crimes committed in Syria I neither saw in Rwanda nor ex-Yugoslavia," she said.
"We thought the international community had learned from Rwanda. But no, it learned nothing."
At first in Syria, "the opposition (members) were the good ones; the government were the bad ones," she was quoted as saying.
But after six years, Ms Del Ponte concluded: "In Syria, everyone is bad. The Assad government is committing terrible crimes against humanity and using chemical weapons. And the opposition, that is made up only of extremists and terrorists."
The commission issued a statement saying it was aware since mid-June of Ms Del Ponte's plans to leave and insisted that its work must continue to help bring perpetrators in Syria to justice.
The resignation shrinks the commission to two members after Thai professor Vitit Muntarbhorn left last year to become the first UN independent expert investigating violence and discrimination based on sexual orientation.
The commission was set up in August 2011 by the Human Rights Council to investigate crimes in Syria, no matter who committed them.
Since then, it has compiled thousands of interviews and keeps a list of suspected war criminals under lock and key at the offices of the UN High Commissioner for Human Rights in Geneva.
But Ms Del Ponte said as long as the Security Council did not put in place a special tribunal for war crimes in Syria, all commission reports were pointless.
The issue of accountability for war crimes in Syria has largely taken a back seat to diplomatic efforts to end the conflict in recent months.
The commission's relevance has also come into question after the UN General Assembly, acting in the face of Security Council inaction, voted in December to set up an investigative body to help prepare legal cases to possibly prosecute the most serious violations in Syria.