Updated | Scott Morrison presents economy as main election issue while Bill Shorten says he will deliver 'a fair go'

Update

Prime Minister Scott Morrison and Labor leader Bill Shorten agree on one thing about the election, which will be held on May 18.

Voters have a clear choice, they said as they kicked off their respective campaigns.

"This election is very straightforward," Mr Shorten said at a news conference in Melbourne.

"It is about being stuck in the past or a bright future and a positive view of what Australians can do together,' he said.

"It is about having a better deal for the future than the one we inherited from the past."

Mr Morrison said voters "have the choice between the government that is delivering a strong economy and will continue to do so, or Bill Shorten's Labor Party, whose policies would weaken our economy".

Update:

Prime Minister Scott Morrison has confirmed the federal election will be held on May 18.

Mr Morrison announced the election at Parliament House after an early morning visit to Governor-General Sir Peter Cosgrove.

Mr Morrison presented the economy as the main issue in the election campaign, and said voters had "a clear choice".

"We live in the best country in the world, but to secure your future, the road ahead depends on a strong economy," he said.

"And that's why there is so much at stake at this election."

Labor Leader Bill Shorten responded on Twitter: "I'm ready to deliver a fair go for Australia. Who's with me?"

Mr Shorten will address the media later in the morning.

Mr Morrison also used Twitter to sum up themes of the Coalition's campaign.

They will be the economy, lower taxes, national security and budget management.

Earlier

Prime Minister Scott Morrison visited the Governor-General Sir Peter Cosgrove in Canberra this morning to ask that Parliament be dissolved.

The election is expected to be held on May 18.

ABC election analyst Antony Green tweeted: "Guessing the plan is to issue writs on Saturday to avoid close of nominations and ballot draw clash with Anzac Day".

There will be four battlefields and some interesting tussles in St George and Sutherland Shire.

Cook: Labor candidate Simon O'Brien has taken on one of the toughest challenges in opposing Mr Morrison, who has a margin of 15.4 per cent as well as being Prime Minister.

Mr O'Brien, 51, has been the bar manager at Woolooware Golf Club for the last 18 years and is a well-known local musician.

Cook extends from the shire across the Georges River as far as Kogarah.

Banks, in St George, is held by Immigration Minister David Coleman by just 1.4 per cent.

His Labor opponent is Chris Gambian, who also stood at the 2016 election.

Hughes, in Sutherland Shire, is considered a safe Liberal seat with Craig Kelly having a 9.3 per cent margin.

However, there is an extra strong move to unseat Mr Kelly by a group called Hughes Deserves Better.

The Labor candidate is Sutherland Shire councillor Diedree Steinwall, who also ran in 2016.

Barton, in St George, is held by Labor frontbencher, Linda  Burney with a 8.3 per margin.

Ms Burney became the first Indigenous member of the House of Representatives when she was elected in 2016.

The Liberal Party has not yet named a candidate..