Lebanon's prime minister has resigned due to an impasse over a new election law and the cabinet's refusal to extend the tenure of the country's police chief.

Najib Mikati said tonight in a speech aired live on TV that he hoped his departure would be "an impetus for leaders to shoulder their responsibilities".

After months of wrangling, the parliament has been unable to agree on a law to govern elections planned for later this year.

The Hezbollah-dominated cabinet has also refused to extend the tenure of Major General Ashraf Rifi, Lebanon's police chief, whom it considers a foe.

Lebanese president Michel Suleiman must accept Mr Mikati's resignation for it to be official.