Remaining allies of Papua New Guinea prime minister Peter O'Neill have objected to his move to seek court action that could delay his resignation.
Mr O'Neill announced two days ago that he would step down this week, after a month of defections from government left him without a majority.
But a day after his announcement, Mr O'Neill filed for a Supreme Court review of a recent planned motion of no confidence in him.
Yesterday his office said he would not formally tender his resignation until the legal application was heard.
This has frustrated a majority of MPs pushing for a vote for a new prime minister, as parliament resumes today.
Former prime minister, Sir Julius Chan, who Mr O'Neill nominated as his replacement, says the move to stop the transition is against the national interest.
Along with another former prime minister and senior MP Paias Wingti, and National Capital Governor Powes Parkop, Sir Julius said the parliament vote must proceed this week without any interference.
"There is a definite mood for change in the country. We met that mood with a decision yesterday (Sunday), and that decision should stand," Sir Julius said, referring to Mr O'Neill's announcement.
But the opposition says it won't believe Mr O'Neill is stepping down until the prime minister tenders his resignation with the governor general.
With an apparent majority of around 62 in the 111-seat house, the opposition group has yet to select its candidate for prime minister.
However, if Sir Julius, Mr Wingti and a group of senior MPs and governors break away from the remnants of Mr O'Neill's field, they could form a third faction with its own nomination.
The situation remains fluid ahead of a probable vote from tomorrow onwards, although the opposition is likely to first try and unseat the Speaker Job Pomat, an ally of Mr O'Neill's.
The Supreme Court has deferred Mr O'Neill's case until Friday but has refused to issue a stay order on any new motion of no confidence being filed in the meantime.