Deputy speaker of parliament Saleh al-Makhzoum said he would complain to the UN special envoy for Libya.
He accused a security force loyal to the officially recognised government in the east of the country of trying to bypass state oil company NOC.
Makhzoum said a tanker had tried to lift crude at Es Sider in the east, according to Reuters.
National Oil Corp (NOC), the state oil firm, had earlier said unknown traders had offered Libyan crude outside the official channels.
