One third of citizens surveyed reported intimidation, one quarter reported that they did not vote – significantly higher rates than in 2012. Less than half reported they voted freely.

Women fared the worst. Only two in five women reported voting freely, with about the same number reporting intimidation. Not a single woman was elected in 2017 to the 111-member parliament.

Haley, who has previously led similar projects for the 2007 and 2012 national elections, highlighted concerns around increasing obstacles facing women voters.

As an example, she cited the case of Koroba in the highlands, where in 2012, she photographed women voting in a relaxed environment. In 2017, the voting area was occupied by men, while women and children looking in from behind a spiked fence.

“The crowd eventually became quite rowdy, tried to push over the fence, objecting that their ballots were being cast for them by other people,” Dr Haley said.

Security forces responded by “driving their vehicles at high speed into the crowd to disperse the crowd … for me, that shows the quite different nature of this election”.

Haley’s team, which included Australian and PNG academics, recorded 204 deaths during the election period – twice as many as were claimed in the 2002 national election, which is often cited as PNG’s worst election. In that poll, the election officially failed in six electorates due to widespread violence and fraud.

“In addition to those [deaths], several hundred people were seriously injured or maimed,” Dr Haley said. “Lots of cases of people having limbs severed, people being chopped [with machetes] across the country, major property damage as well.” Of the 43 electorates scrutinised by observers, there were only six in which there was no death or major property damage.

The ANU conclusions, drawing on reports by Australian and PNG academics, echo the conclusions of a report by Transparency International PNG, which found the 2017 election “flawed to an unforgiveable extent”.

But they are markedly more critical than previous observer reports, including by the European Union, the Commonwealth Observer Group, and the Melanesian Spearhead Group,.

ANU academic and Papua New Guinea election specialist, Bill Standish, said that when foreign observers turn up at polling stations, people tend to be on their best behaviour and that dirty tactics had spread since 1992.

“Efforts towards free and fair elections have been swept aside by the control which MPs exert over local officials and even police,” he said.

“Popular democracy has been replaced by cynical manipulation by incumbents, their rivals and supporters alike. Observers’ reports, social media outrage and electoral appeals all seem to have no effect.”

Haley’s teams also reported that counting had also been compromised.

“In tally rooms across the country, officials employed what observers called a bulldozer approach to counting, which meant not doing quality checks … deflecting questions and queries from scrutineers.” Prime minister O’Neill has asked for a review of preferential voting because of the slow and costly count.

The PNG Electoral Commission and national government did not respond to The Guardian’s requests for comment.