The head of Libya's internationally-recognized parliament has criticized the UN envoy, accusing the international community of imposing a unity government that contradicts a UN-brokered agreement.

Agila Saleh told Libya 218 television on Tuesday that UN envoy Martin Kobler is acting as the country's "ruler" and paving the way for a new unity government to seize power in the capital before parliament votes on it.

The parliament is expected to vote on the unity government on April 18.

Western nations hope the UN-backed government led by Fayez Serraj, a little-known technocrat, can unite the country and combat an increasingly powerful Islamic State group affiliate.