Tonga's Prime Minister Hu'akavameiliku Siaosi Sovaleni has resigned his leadership ahead of a vote of no confidence.

In an address to parliament this morning, he announced he would step down as Prime Minister effective immediately.

He will stay in Parliament as an MP.

The vote of no confidence against him was brought by MP 'Aisake Eke, who claimed to have the numbers.

Sovaleni has faced a number of challenges this year, resigning as defence minister in April after King Tupou VI withdrew his confidence in him.

Then, in September, he narrowly survived a vote of no confidence.

In August, Tonga hosted the regional Pacific Islands Forum leaders meeting and Sovaleni played a key leadership role. He also recently returned from New Caledonia where he led a high level regional mission to offer support with the unrest there.

Speaker of the House Lord Fatafehi Fakafanua is expected to announce the next step in electing a new Prime Minister.