Proposal for multinational operation to oversee truce comes as fighting grew more complex by the day

The UN security council has passed a resolution mandating a multinational operation to oversee a ceasefire in Libya, despite serious doubts that any of the conflict’s key players will abide by its terms.

The UK-backed resolution, calling for a ceasefire without preconditions and an immediate end to the supply of arms to both sides, was passed by 14 votes to zero, with one abstention from Russia.

It was seen as a test of the UN’s waning authority after its secretary general, António Guterres, described offensives by both sides in the war as a scandal.

A UN arms embargo is being flouted with impunity and plans for an EU naval mission to monitor illegal arms shipments has not yet been agreed.

The UN’s ability to influence events on the ground has been further weakened by the refusal of Gen Khalifa Haftar, the leader of the self-styled Libyan National Army, to grant landing permissions for UN staff travelling to Libya. The UN has complained that the ban is severely hindering its efforts to help Libya’s most vulnerable people.

World leaders gathered in Berlin last month to make a high-profile call for a truce, but subsequent military talks in Geneva and a parallel political track in Cairo have so far made limited progress on the terms of a ceasefire, the role of monitors and wider issues such as the distribution of oil revenues between the west and east of the country.

Libya’s conflict pits Haftar’s LNA, based in the east of the country, against the UN-recognised Government of National Accord, which is headed by the prime minister, Fayez al-Serraj, and based in Tripoli in the west. There has been sporadic fighting since a power vacuum emerged after the fall of Muammar Gaddafi in 2011, but the conflict escalated last year when Haftar announced his intention to capture Tripoli.

Haftar’s forces are supported by the United Arab Emirates, receive logistical help from Egypt and are bolstered by hundreds of Russian mercenaries. The LNA also has political support from France. The GNA’s main backer is Turkey.

Since 18 January, Haftar has blockaded oil ports in a successful attempt to deprive the GNA of revenues it needs to pay public sector workers. Oil production has fallen from 1.1m barrels per day to below 200,000 and the country overall has lost $1.3bn in revenues.

Key figures from the UAE who were in London this week to meet British ministers showed no sign that they were willing to abandon Haftar, although the UAE insists there is no military solution to the conflict and has not endorsed Haftar’s move to capture Tripoli.

The UAE claims Serraj is a weak puppet of Tripoli’s Islamist militia, which feed off oil revenues supplied by the Libyan Central Bank.

Although Haftar controls the oilfields, the revenue from oil exports is gathered by the National Oil Corporation, which passes it on to the central bank for distribution across the country. So far international action has prevented Haftar from exporting oil independently and keeping the revenue. One of Haftar’s many demands is the removal of the central bank governor, Sadiq al-Kabir.

The fighting in the country has grown more complex owing to the arrival of Turkish-financed mercenaries from Syria to help the GNA, and Russian-backed mercenaries to support Haftar. The GNA says it is deeply frustrated by the failure of the international community to call out the UAE’s support for Haftar earlier, leaving the GNA’s leaders to look to Turkey for support.

The UK haS been consulting for weeks on the terms of its UN resolution. The resolution called on the African Union, the Arab League and the EU to help supervise a ceasefire and would urge the Libyan parties to resume a political dialogue.

The resolution will require the approval of at least nine of the 15 security council members. The council’s five permanent members – Russia, the US, France, Britain and China – each have veto powers.