Prime Minister Jacinda Ardern has announced a general election date during a post-Cabinet press conference.

The 2020 general election will be held on 19 September.

As well as electing a new government, voters will be asked to decide on voluntary euthanasia and the legalisation of cannabis through two referenda.

She said for politicians, a three-year term meant "we are always in campaign mode anyway".

"This year we intend to govern right up until the election is held which I can advise will be on 19 September."

She said Labour was asking for a further term to "keep getting the job done".

"We are running an established and effective MMP government and overseeing a strong economy with low unemployment and growth rates that others look to with envy."

Ardern re-iterated that Labour's intention was to deliver a "positive and factual election campaign".

"The Labour Party signed up to Facebook's new transparency rules. I stand by these actions as prime minister and as the leader of the Labour Party."

Watch the PM's press conference here:

Ardern has advised the Governor-General of the election date.

The House will rise on Thursday, 6 August and Parliament will be dissolved on Wednesday, 12 August.

Writ day will follow on Sunday, 16 August, and nominations will close at noon on Friday, 21 August. Advance voting will start on Monday 7 September.

Subject to the passage of the Electoral Amendment Bill currently before the House, the last day for the return of the writ will be Thursday, 15 October.