The Maori Party is expected to decide within days whether it will challenge Hone Harawira in the byelection he is forcing in the Te Tai Tokerau electorate, even though the MP claims it assured him it would not.

The party's co-leader Pita Sharples has also challenged Mr Harawira to prove he has a mandate by standing against the Maori Party, rather than trying to escape the collision.

Mr Harawira confirmed at the launch of his new Mana Party that he would resign this week to force a byelection, saying it would give the people of Te Tai Tokerau their say on whether he still had a mandate as the new party leader.

Mr Harawira also said the Maori Party president had confirmed it would not stand against him, in accordance with the agreement reached when he left the party in February.

Yesterday, however, Maori Party president Pem Bird said he considered the agreement was "no longer in force" because those assurances related only to a general election and only if Mr Harawira stood as an independent.

Dr Sharples also said on TVNZ's Q+A that the decision to call a byelection had broken the truce between the two parties.

He also disputed that Mr Harawira could claim to have a mandate from Maori if the Maori Party did not stand against him.

Mr Bird said the party's national council would meet within days to decide whether to stand.

However, he considered the byelection a waste of time and money.

"The only mandate that counts is in November. I think everyone agrees it's a colossal waste of taxpayers' money and given the particular times we are going through, it's not a particularly good look, I would have thought."

Mr Harawira's byelection plan has also left the Labour Party with a difficult decision.

Labour leader Phil Goff said it would decide soon whether to stand. However, he said the byelection was a total waste of money because the selected MP would be in Parliament for only a few weeks before the House rose for the election campaign.

"There is no need, no demand, for a mandate. There is nothing to prove there. This is just a stunt to launch his election campaign."

Mr Goff said he was astonished Mr Harawira would use up more than $500,000 that would have been better spent on issues such as Maori health and education.

He doubted Mr Harawira's party would have as much of an impact as Mr Harawira believed.

"Will [Maori voters] go for an extreme option - Hone Harawira and the people he's got around him?

"It's not my impression Maori will go for an extreme option."

If both the Labour Party and Maori Party refuse to stand against Mr Harawira, it would blunt his claims to have gained a mandate from his people to represent them under his new party.

Refusing to stand in the byelection would also put more pressure on Mr Harawira to defend his own turf in the general election, cramping his ability to raise support for his Mana party nationally.

However, refusing to stand in the byelection could open Labour to claims, at least from Mr Harawira, that it had either given up on the seat or did not care about it enough to fight for it.

Green Party co-leader Metiria Turei said a final decision was yet to be made, but her party was unlikely to stand in the byelection, despite contesting all others this term.