PAPUA New Guinea's government is engaging in "constitutional terrorism" over a proposal to toughen the rules for votes of no confidence, Opposition Leader Belden Namah says.
Prime Minister Peter O'Neill last week proposed the changes to make sure motions of no confidence are made public three months before they come to a vote, as well as reducing the minimum annual number of parliamentary sitting days.
"The prime minister has yet to specify publicly as well as in the proposed amendments, the public interest or national goal that the amendments... achieve, promote or enhance," Mr Namah said in a statement.
"The prime minister ought to be clear that manipulating the constitution to avoid or escape the scrutiny of parliament, does not constitute a public but a selfish interest.
"This is effectively constitutional terrorism".
Mr Namah said he will launch legal action to stop the amendments being discussed in parliament, which resumes on Tuesday following a six-week break.
The opposition leader said he wanted all further constitutional amendments to be subject to a referendum, and for tougher separation of powers between the legislative and executive branches of government.
Mr O'Neill's proposed changes will also require one third of parliament to mount a motion of no confidence instead of the currently required one 10th.
The amendment appears to reduce the minimum required parliamentary sitting days to 40, down from 63.
Finance Minister James Marape says the amendments are necessary to promote political stability.
"We only have to look at nations like Singapore, Malaysia, Thailand, Indonesia, South Korea, who all through political stability have progressed," Mr Marape told the Post Courier Newspaper.
"Yet in the same period of time prior to 2002, the average life of our governments has been 18 months.
"I give assurance that the proposed laws will be brought in with safety valves in as far as protecting our nation from potential of abuse of office by leaders."
Mr Marape said the government will engage in community consultation before the laws are brought to a vote.
Earlier this year Mr O'Neill convinced his parliamentary supporters to pass a law banning votes of no confidence for the first 30 months out of a five-year term.
PNG spent the second half of 2011 and much of 2012 mired in a political impasse sparked by the dumping of long serving prime minister Sir Michael Somare.
Since the election last year Mr O'Neill has governed PNG with an overwhelming parliamentary majority of 95 MPs out of 111.