Agailah Saleh, the speaker of Tobruk-based House of Representatives, has threatened to sue the United Nations over its support for the UN-proposed government, London-based Alhayat newspaper reported on Wednesday.

In an unprecedented step, Agailah sent a letter to UN Secretary General Ban Ki Moon threatening to file a complaint against the United Nations to the International Court of Justice if the UN insisted on backing Fayaz Sirraj's government without a vote of confidence from the parliament.

On Sunday, Tobruk parliament rejected to give confidence to the UN-proposed government and asked the Presidency Council to form a mini-government of around 12 ministers in just 10 days; otherwise, the parliament will call for PC replacement.

In his letter, Agailah accused the UN of violating Libya's constitution and imposing a number of politicians to govern the Libyan people.

"The UN knows very well that so-called government of national accord does not legally exist, there is only a Presidency Council that did not win a vote of confidence, and it does not meet with all of its members," Agailah said in his letter, according to Alhayat.

He also expressed anger over the invitations sent to what he described the uncompleted Presidency Council to represent Libya in the international arena without being approved by the parliament.