Papua New Guinea's prime minister Peter O'Neill says the opposition has been deceived by misinformation about the PNG Sustainable Development Program or SDP.
Another war of words over SDP has erupted after a recent Singapore High Court ruling quashing the PNG government's claim to the Singapore-registered Programme with assets worth about $US1.4 billion.
SDP was set up as a divestment vehicle for Western Province's lucrative Ok Tedi copper and gold mine, and has a long term fund for the people of the province.
The opposition leader Patrick Pruaitch accused Mr O'Neill of trying to derail social and economic development programmes sponsored by SDP in Western Province.
"PNGSDP is a model entity that operates like a sovereign wealth fund. It has done an excellent job in nurturing its long-term fund which now stands at over K4 billion," Mr Pruaitch said.
"PNGSDP has been transparent in its operations and has published fully audited annual reports since its establishment in 2002."
Mr Pruaitch alleged the Prime Minister wanted to control and squander the lucrative long-term fund.
But Mr O'Neill said characterisation of the fund as a type of charitable fund was a lie.
He warned that the SDP is a private company that is not accountable to anyone in Western Province or any government oversight agency.
Mr O'Neill has indicated the government would appeal the Singapore court ruling.
"Our Government will continue to pursue this matter to ensure control of the funds is given to the people of Western Province, and to bring to justice those who have acted in a criminal manner.
BHP Billiton's divestment in 2001 followed legal action by Western Province landowners over extensive and long lasting environmental damage caused by the mine operations, particularly its riverine tailings disposal system.
"The environmental devastation that came from the Ok Tedi mine, under the control of BHP as one of the world's largest companies, killed and poisoned thousands of our people, "Mr O'Neill explained.
"The PNGSDP money was supposed to help rebuild lives and must be given to the people of Western Province."
The prime minister has focussed on the involvement with SDP of his political rival, opposition MP and former prime minister Sir Mekere Morauta.
"A recent companies search confirms that Mekere Mourata, and three other individuals, are shareholders of this private company in Singapore," the Prime Minister said.
Mr O'Neill claimed there was no trust arrangement on behalf of the people of Western Province or the Western Provincial Government.
"This all goes against the promise Mekere Morauta made that PNGSDP would be established to hold shares in trust for communities in Western Province.
"The Leader of the Opposition should research these facts, and stand up for the rights of the people of Western Province instead of supporting the people behind these criminal acts."
However, the Singapore High Court found that PNG's government had failed to prove that it controlled a charitable trust that entitled the state to intervene and control SDP.
"This is a blatant money grab by Mr O'Neill who has spent millions in public funds to pursue this case in Singapore," Mr Pruaitch said.
Mr Pruaitch said he concurred with the view of the four Western Province MPs that the Prime Minister should stop attacking PNGSDP.
He urged the government to work with that organisation and the Provincial Government "to ensure that the interest income from the Long-Term Fund is spent to achieve development and change in Western Province.
Meanwhile, Mr Pruaitch has defended SDP against government criticism about its development achievements in Western Province.
He said among the many things SDP has done, it had spent tens of millions of dollars to upgrade dozens of schools.
It had also repaired and upgraded the telecommunications network so almost everyone in the province now can access 4G phone and internet services.