Australians will head to the polls on 18 May, the prime minister Scott Morrison has announced, firing the starting gun on an election campaign that immediately saw both major party leaders vie to offer a uniquely Australian vision – a society and economy that gives everyone a “fair go”.

Setting out his economic credentials, Morrison earlier said the choice for voters was “between enterprise and envy”, and that electing a Labor government, led by rival Bill Shorten, would be “an economic leap in the dark”.

Morrison, who leads the ruling centre-right Coalition government, said on Thursday morning: “I believe in a fair go for those who have a go. And what that means is, part of the promise that we all keep as Australians is that we make a contribution and don’t seek to take one.”

Hours later, Shorten said: “What we believe in is making sure that the economy works in the interests of working and middle-class people, when everyday Australians are getting a fair go, this economy hums.”

He added: “We also want to make sure that women get a fair go in our society.”

Climate change and immigration are also key issues but serious divisions within Morrison’s Liberal party – which rules in coalition with the National party – will also be at the front of voters’ minds. The Coalition has held power since 2013 but is polling in second place after years of factional infighting and inaction on climate change.

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Morrison, a former treasurer, took over as prime minister after toppling his more moderate predecessor, Malcolm Turnbull, in 2018. Turnbull himself wrested the prime ministership from his Liberal rival Tony Abbott in 2015.

The Liberal party has also been shaken by a series of high-profile resignations, accusations of bullying, and an embarrassing byelection result that saw the party lose the seat previously held by Turnbull to an independent candidate, leaving the government without a majority in the House of Representatives.

The Coalition has been behind in the polls since mid-2016, though the last Guardian Essential poll had Labor’s lead narrowing of 52% to 48%.

Facebook Twitter Pinterest Opposition leader Bill Shorten. Photograph: Tracey Nearmy/Getty Images

The party’s troubles intensified in August when Turnbull was dumped over his energy policy, which split the party between moderates and pro-coal conservatives who were opposed to any action that would see Australia move away from coal-fired power stations.

The Coalition has since faced criticism for its lack of gender diversity. While 42% of Labor’s federal parliamentarians are women, for the Liberals the figure is 21% and the Nationals just 14%. One female Liberal MP reportedly cautioned Morrison last year that the party was viewed as “homophobic, anti-women, climate change deniers”.

Morrison has tried to frame the election as being about economic management.

“We live in the best country in the world, but, to secure your future, the road ahead depends on a strong economy,” he said on Thursday morning. “And that is why there is so much at stake in this election.”

While the election was called on Thursday, the nation has been in unofficial campaign mode for several weeks. During that time the public have been treated to photographs of the Australian treasurer as a young man, shirtless and with a mullet; Captain Getup, a fake superhero created by a conservative lobby group to parody a leftwing lobby group; and Morrison claiming the Labor party had declared a “war on the weekend” by falsely stating that as part of its electric vehicles policy the party would tax four-wheel drives and utility vehicles, stopping people from taking out their caravans or boats.

Morrison’s treasurer, Josh Frydenberg, delivered a budget for the country on 2 April in which his government predicted that the Australian economy would return to surplus for the first time in a decade.

Frydenberg taunted Labor, telling parliament that the last time Labor had delivered a surplus, which was in 1989, he had had a mullet. The treasurer, who is now bald, provided photographs to the Murdoch-owned Australian newspaper, showing him in his 20s, including one picture showing Frydenberg lying in bed half-naked embracing three tennis rackets.

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Morrison is Australia’s first Pentecostal prime minister, and comes from the conservative southern suburbs of Sydney. He is known for his “daggy dad” persona, a preponderance for wearing different baseball caps, and a tendency to overuse Australianisms such as “fair dinkum”. As director of Tourism Australia, Morrison oversaw the much-mocked “Where the bloody hell are you?” advertising campaign.

As immigration minister under Tony Abbott, Morrison was one the one of the architects of Australia’s notoriously harsh border protection policies, which he has not backed away from since becoming prime minister. On a desk in his office, Morrison has a model of a migrant boat made out of metal, with the lettering “I stopped these”.

In February and March, Morrison seemed to be trying to make the election about immigration, saying sick refugees who were brought to Australia for treatment would “take the place” of Australians needing care.

Facebook Twitter Pinterest Former Australian prime minister Malcolm Turnbull. Photograph: Dan Himbrechts/AAP

Morrison was accused of trying to start a scare campaign. “Like a pair of petulant schoolboys they are running around with a box of matches trying to light fires,” said independent MP Kerryn Phelps of Morrison and one of his ministers.

Morrison’s opponent, Bill Shorten, a former union leader, has had consistently poor personal approval ratings, but support for the Labor party has remained strong.

Labor has committed to an ambitious policy platform, including controversial tax reforms that would see loopholes for property investors close, and more serious action on climate change, including a renewable energy target of 50% by 2030.

Election analysts will be keeping a close eye on minor parties in the election, including far-right One Nation, which is predicted to win 5% of the vote, and has been condemned for inciting racial hatred.

The Greens party, which has frequently opposed the government on matters including environment and refugee policy, is polling at 11%. Other parties and independents, who have found themselves powerful in the minority government of the past six months, are polling at 10%.