Newshub understands the Labour Party will sign up to Facebook's transparency tool, known as the Facebook Ad Library Report, that shows voters where campaigning money is being spent on Facebook ads.

The only other party in New Zealand to have signed up is the Greens.

Ardern, leader of the Labour Party, said the retreat kicked off on Wednesday with "conversation around what we want the election to look and feel like for us as a team", which she said was a "really important place" to start.

The Prime Minister said those were "all values and principles that were really important to us in the last election and will be central for us again this election".

She spoke of the "importance of us campaigning positively around the progress that we have made but where there is work still to be done - and there is - that we want it to be robust where there is a good exchange".

Ardern came to power in 2017 - a year that was defined by the phrase "fake news" by dictionary publisher Collins, after being popularised by US President Donald Trump.

Facebook is expected to be the main "fighting ground" for political parties in New Zealand this year, despite findings released in 2019 that said fake news and propaganda are still rife on the online platform.

Ardern said it is "incredibly important it is for us as the Labour Party that New Zealand does not fall prey to what we've seen happen in other jurisdictions".

The campaign manager for former US presidential candidate Hillary Clinton has warned that the 2020 New Zealand election could be a "juicy target" for a major cyber hack.

The Prime Minister has said she supports Twitter's ban on paid political advertising, saying voters need to be able to rely on what they are seeing during political campaigns.

The 'huge' infrastructure spend

Ardern said Labour members at the caucus retreat will be getting an economic overview from Finance Minister and Labour MP Grant Robertson.

She said Robertson will be touching on the major $12 billion infrastructure package announced by the Government last month, the full details of which haven't yet been released.

"Just to give everyone a scale of that investment, that is roughly three times the amount of new capital spending that you'd see in a Budget - in one go, outside of a Budget cycle," Ardern said. "It is huge."

"The time to do it is right. We have infrastructure needs in New Zealand and we also have low debt and we're also at a point where borrowing is incredibly cheap."

The money to pay for those projects will be borrowed from banks and international funds that will be paid back over time, as the economy is expected to pick up over the next few years.

"The IMF has said now is the time and that is what we are doing as a Government to invest in the areas where we have significant infrastructure deficits," Ardern said.

"This is going to be a significant year for New Zealand, a significant year for us, and I know as a team we're feeling incredibly positive about the year ahead and the potential of what we will continue to deliver as a Government as we continue to govern."

Last year's Labour Party caucus retreat was defined by Ardern's speech in which she labelled 2019 the Government's "year of delivery".