The president of the Libyan parliament that is not recognised internationally said on Wednesday that lawmakers preparing to sign a UN-sponsored unity government agreement in Morocco had no legitimacy.
The international community has been pressuring the North African nation's two rival administrations to form a unity government amid concerns about the rise of the Islamic State group there.
Libyan parliamentarians are due in the Moroccan resort of Skhirat on Thursday to sign the deal in a ceremony a Moroccan diplomat said would take place at 1100 GMT.
But Nouri Abusahmein, who heads the Islamist militia-backed General National Congress in Tripoli, said the signatories would have no legitimacy.
"Whoever has not been commissioned by the GNC to sign or initial a deal on its behalf is, and will remain, without legitimacy," he said before the GNC in the capital.
A government such as that proposed by the United Nations "is not the subject of consensus and does not even guarantee the minimum required to ensure its effectiveness", he added.
On Tuesday in Malta, Abusahmein met Aguila Saleh who heads the internationally recognised parliament based in Tobruk in the east near the border with Egypt.
It was the first time they had met since the rival administrations were formed in 2014.
At a joint news conference, both men said that those who sign the agreement represent only themselves.
They said Thursday's signatories, although members of the respective parliaments, would not be acting as official representatives of those bodies.
At the beginning of October in Skhirat, delegations from both sides approved a draft agreement negotiated under the auspices of the UN, but it was later rejected by their parliaments.
On December 6, members of the two bodies launched an alternative process in Tunis by signing a "declaration of interest" on a unity government, and this process is backed by the two parliament heads.
Libya has been mired in chaos since the 2011 overthrow and killing of long-time dictator Muammar Gaddafi.
ISIS militants have exploited the lawlessness to expand their presence there.