KATHMANDU (AFP) - Nepal's former ruling Maoists threatened to embark on a wave of street protests on Wednesday as the newly-elected parliament convened for the first time to begin work on drawing up a post-war constitution.

Party leaders have set themselves a 12-month deadline to reach a consensus on a draft constitution, promising to overcome their outstanding differences eight years after the end of a decade-long civil war.

But a senior member of the Maoists, which suffered a humiliating defeat in a Nov 19 general election, warned his party's resolve should not be underestimated despite its reduced presence in the constituent assembly, which doubles up as a parliament.

"We will have to be vigilant and may resort to street protests to ensure that our agendas are addressed by the constituent assembly," Mr Ganesh Man Pun told AFP on Wednesday ahead of the formal opening ceremony.

The Maoists only reluctantly agreed to take part in the assembly after initially threatening to boycott it over accusations of electoral fraud.

They were soundly beaten by both the first-placed Nepali Congress and the Unified Marxist-Leninist (UML) parties who are still locked in negotiations about forming a new coalition government.

The Maoists won the last elections in 2008 by a landslide, only two years after signing a peace agreement to end their 10-year uprising against the monarchy. As part of the deal, King Gyanendra agreed to stand down.

But the ensuing four years were marked by a series of short-term coalition governments, mainly led by the Maoists, and the first assembly broke up amid rancour in May 2012.

Congress leader Gagan Thapa said that politicians would not miss a second opportunity to reach a deal which would effectively complete Nepal's peace process.