The vote count in Australia’s general election is proving closer than opinion polls had predicted, with the ruling conservative coalition appearing more likely to form a government than the favoured centre-left opposition party.

Opposition Labour Party deputy leader Tanya Plibersek had said in early counting that she was “more cautiously optimistic than confident”, but she predicted a tighter result as counting progressed.

“The only thing you can say about tonight is it’s likely to be a very late night,” she said.

It was not clear whether the results would be available by the end of vote counting on Saturday.

Opinion polls had suggested that the conservative Liberal Party-led coalition would lose its bid for a third three-year term, and that Scott Morrison would have had one of the shortest tenures as prime minister in the 118-year history of the Australian federation.

Opposition leader Bill Shorten said on Saturday morning that he was confident Labour would win, but Mr Morrison would not be drawn on a prediction.

Mr Morrison is the conservatives’ third prime minister since they were first elected in 2013. He replaced Malcolm Turnbull in a leadership ballot of government colleagues in August.

Tony Abbott, who became the first of the three conservative prime ministers in the 2013 election, conceded defeat in the Sydney seat he has held since 1994. “The good news is that there is every chance that the Liberal-National coalition has won this election,” he said.

Polling suggests climate change was a major issue in the seat for voters, who elected an independent candidate, Zali Steggall.

As prime minister in 2014, Mr Abbott repealed a carbon tax introduced by a Labour government. He was replaced by Mr Turnbull the next year because of poor opinion polling, but he remained a government legislator.

Mr Morrison began the day by campaigning in the island state of Tasmania, where the Liberals were making gains in Labour-held seats. He then flew 560 miles home to Sydney to campaign and vote.

Mr Shorten contained his campaigning to polling centres in his home city of Melbourne, where he voted on Saturday morning.

He said early in the day that he expected Labour would start governing from Sunday. He said his priorities would be to increase wages for low-paid workers, hike pay rates for working Sundays and reduce Australia’s greenhouse gas emissions

Mr Shorten has been campaigning hard on more ambitious targets to reduce Australia’s greenhouse gas emissions.

The government has committed Australia to reduce its emissions by 26%-28% below 2005 levels by 2030. Labour has promised a 45% reduction.

Mr Shorten, a 52-year-old former union leader, has also promised a range of reforms, including the government paying all of patients’ costs for cancer treatment and a reduction of tax breaks for landlords.

Mr Morrison, a 51-year-old former tourism marketer, said he had closed Labour’s lead in opinion polls during the five-week campaign and predicted a close result.

He promises lower taxes and better economic management than Labour.