Dozens of survivors and more than 50 non-government organisations have called for a UN investigation into last year's deadly Beirut port blast.
More than 200 people died in the explosion in August.
In a joint letter, 53 international and Lebanese NGOs, as well as 62 survivors and relatives of people killed in the blast, accused Lebanon's authorities of failing to conduct a transparent and thorough investigation almost 10 months on.
The investigation has been beset by delays.
In February, Fadi Sawan, the judge who was leading the probe, was removed after he accused two former ministers of criminal negligence.
"The ten months since the blast have been marked by the authorities’ obstruction, evasion and delay," the letter reads.
It added that several NGOs had “documented a range of procedural and systemic flaws in the domestic investigation that render it incapable of credibly delivering justice, including flagrant political interference, immunity for high-level political officials, lack of respect for fair trial standards, and due process violations.”
The letter said that, given local authorities' failings, only the UN would ensure the rights of victims were protected.
“It is time for the Human Rights Council to step in, heeding the calls of the families of the victims and the Lebanese people for accountability, the rule of law, and protection of human rights,” it reads.
“The Human Rights Council has the opportunity to assist Lebanon to meet its human rights obligations by conducting an investigative or fact-finding mission into the blast to identify whether conduct by the state caused or contributed to the unlawful deaths, and what steps need to be taken to ensure an effective remedy to victims.”
Aya Majzoub, Lebanon researcher at Human Rights Watch, said without a thorough investigation, the country could be at risk of further tragedy.
“The Beirut port explosion was not an isolated or idiosyncratic incident. Rather, it was one highly dramatic illustration of the human rights impacts of decades of corruption, incompetence, impunity and mismanagement by Lebanon’s ruling elite,” Ms Majzoub said.
“Without accountability for this explosion, there is nothing stopping another disaster from happening.”
The call for an international investigation comes barely a week after the Special Tribunal for Lebanon, a UN court set up to probe the assassination of former Prime Minister Rafik Hariri in 2005, was forced to call off a landmark trial amid a funding crisis.
Salim Ayyash, who was already found guilty in his absence by the court of assassinating Mr Hariri, was due to stand trial for three other attempted killings this week.
His trial was, however, cancelled earlier this month.