SYDNEY, Australia—Former finance minister James Marape, a critic of a major global gas development deal, was elected by parliament as the new prime minister of Papua New Guinea on Thursday after weeks of turmoil over the handling of the South Pacific nation's resource riches.

Marape became prime minister by an overwhelming majority of 101 votes to eight in parliament in the capital, Port Moresby, a day after Peter O'Neill resigned having lost the support of the house after seven years in power.

Speaker Job Pomat declared Marape as prime minister-elect and then suspended parliament so Marape could be sworn in by Governor-General Bob Dadae. Lawmakers surrounded Marape to congratulate him.

Marape was supported by members of O'Neill's government but it was not immediately clear whether there would be ministerial or policy changes. Marape quit as finance minister in April, questioning a gas deal with France's Total SA.

Political instability is not unusual in poverty-stricken but resource-rich PNG but Marape's defection from the government tapped into growing concern over governance and resource benefits not reaching the poor.

Those concerns ultimately led to O'Neill's downfall.

Marape and his allies have indicated that an agreement struck with Total in April, which allows Total, Oil Search Ltd and ExxonMobil Corp to begin work on a $13 billion plan to double gas exports, could be reviewed.

"Agreements and resources laws will be relooked at as a matter of priority," Philip Undialu, a lawmaker aligned with Marape, told Reuters by text message.

"It's going to be a fair deal not necessarily radical," he said.

Marape told PNG's National newspaper two weeks ago, in reference to the April deal, that "something is wrong somewhere when the government is not unlocking ... resources for our people."

"We have a government that wants to save the interests of corporate giants," he said.

The political uncertainty has knocked almost 6% from shares in Oil Search, an Australian partner in large liquefied natural gas developments in PNG, since the challenge to O'Neill gained traction on Friday.

Business leaders and another development partner, Santos Ltd., dismissed immediate concerns but said political developments would be watched closely. Oil Search shares rose 0.4%  in early trade in a falling broader market.