The Papua New Guinea opposition MP Belden Namah says the government must respect the outcome of the Bougainville referendum.
Bougainville, an autonomous region of PNG, is to hold an independence referendum in October this year.
PNG's prime minister Peter O'Neill this month stressed that after the vote was not binding.
PNG's national parliament would debate the matter and decide the final outcome.
However, the Vanimo Green MP Belden Namah said PNG must respect the will of the people of Bougainville.
"We've got to respect which ever way they go, whether it's for greater autonomy or independence, as long as the outcome is lasting peace for the people of Bougainville," Mr Namah said
"The (PNG) goverment would make a terrible mistake to try and go against the wishes of the people."
Mr Namah, a former deputy prime minister under Mr O'Neill, said he had great affection for Bougainvilleans, and understood well the suffering they have been through.
The MP served in the Bougainvlle civil war as an oficer in the PNG Defence Force, and was sent to prison with two fellow officers for resisting an intervention by mercenaries in the notorious Sandline Affair.
"We're talking about lives, we're talking about an island that has gone through a lot of suffering," he said.
Mr Namah was frustrated with the PNG government for delaying the referendum's date by four months.
A meeting at the start of this month in Port Moresby between the PNG national government and the Autonomous Bougainville Government resolved to defer the referendum to 12 October.
"We have to follow the (Bougainville) peace process and get this referendum over and done," he said.
"If PNG as a country has got no money to fund the referendum, please talk to the Australian government, talk to the New Zealand government, talk to the United Nations."