HETAUDA, Nepal (AFP) - Thousands of Nepal's former rebel Maoists gathered on Saturday for their biggest show of strength since taking up arms in a 10-year insurgency and toppling the world's last Hindu monarchy.

Party leaders who swept to power in 2008 elections following a peace deal, are using a general convention in the southern industrial hub of Hetauda to shore up grassroots support amid growing disillusionment among the rank-and-file.

Around 3,000 delegates from across the Himalayan nation attending the party's first convention in 21 years will hear opening speeches from the party's charismatic leader Pushpa Kamal Dahal and Prime Minister Baburam Bhattarai.

Among issues up for discussion will be the formation of a new federal structure for Nepal as well as the ending of gender and caste-based discrimination, said Finance Minister Barsha Man Pun.

"We were able to bring about such radical transformation in Nepali state apparatus even as the third-largest party 21 years ago," he told the English-language Republica daily newspaper.

"Now, as the largest party, the impact of our general convention in shaping the national politics, economy and society will be even greater."

The five-day meeting opened amid criticism from New York-based Human Rights Watch of Nepal's Maoist-led government over its lack of progress on human rights over the last 12 months.

The group said in its World Report the rights of women, children and Tibetan refugees had been neglected while government rhetoric on equality for lesbian, gay, bisexual and transgender people had "exceeded actual implementation".

"2012 was a sorry replay of Nepal's past seven years of impunity and government unwillingness or inability to deliver on its commitments to human rights," said Brad Adams, the organisation's Asia director.

An estimated 16,000 people died in the 1996-2006 conflict fought by the Maoists against the monarchy, which was deposed when the rebels turned to mainstream politics and took power in elections.

"There appears to be collective amnesia among Nepal's policymakers about the inequities and injustice that helped fuel the conflict in the first place," Adams added.

In-fighting, including a split in the party last year, has confounded efforts to draw up a post-conflict constitution spelling out how Nepal should be run.

An interim assembly elected for the task was dissolved in May and the Maoists now lead Nepal as the major partner in a shaky caretaker coalition which has had little power to make fundamental policy decisions.

Party leaders will try to ensure the support of former cadres struggling to rejoin civilian life after the war, many of whom have complained of a sense of betrayal that their sacrifices have been forgotten.