The former president and treasurer of the New Zealand First Party, Lester Gray and Colin Forster, want to appear before the justice committee to reveal what they know about the party's donations.

"We want to shed some light on the inappropriate internal workings of the party that seemingly aren't monitored or controlled by electoral law," the pair said in a joint letter to the committee.

"Our major concern is that the party affairs have effectively been taken over by the caucus [despite] public comments saying the opposite."

The justice committee will tomorrow decide whether to allow them to appear or not.

The letter to the committee seeking an appearance was released by National's electoral spokesman Nick Smith, who is a member of the committee.

"The committee needs to be aware that we face substantial legal and personal threats should we make public statements on these issues," the letter says.

It said the committee's inquiry into the 2017 election would be a "safe place for us to disclose our knowledge of what has taken place."

"We are happy to make our submission to a closed committee without New Zealand First officials present and will make ourselves available at the earliest opportunity."

Smith said he had had Gray and Forster's blessing to release the letter.

Nick Smith's distribution of the letter follows a row in Parliament today in which New Zealand First leader and Deputy Prime Minister Winston Peters accused National in Parliament of failing to declare $100 million of donations.

Parliament was debating a political donations bill under urgency which reduces the amount of donations foreign entities or people can make from $1500 to $50.

National supports the bill but has complained that it is bypassing a select committee and that it does not cover trusts and foundations of the type that New Zealand First - and National - have.

Stuff recently reported that it had received a bundle of documents from the New Zealand First Foundation showing donations it had received from "wealthy investors, horse racing figures, food magnates, and property juggernauts."

The foundation has lent money to the party and it has been repaid but it has not divulged the donors to the foundation.

Stuff reported that the NZ First Foundation received almost half a million dollars between April 2017 and March this year.

The Electoral Commission is looking into the foundation, which is run by the party lawyer Brian Henry and former president Doug Woolerton.

A National Party donation is being investigated by the Serious Fraud Office after a complaint to the police by former National MP Jami-lee Ross.

During debate on the bill, Peters, protected from defamation because of Parliamentary privilege, accused National of having $100 million worth of donations that they have never declared.

"They have the gall and the audacity to rise in this Parliament and condemn with attempts of innuendo and slight, a party [NZ First] that has behaved within the law and will be proven to be so."

Earlier in the debate Smith had been critical of the New Zealand First Foundation which Peters insists is doing nothing unlawful.

"In respect to NZ First Foundation, this matter is being examined by the very authorities qualified to do so," Peters said in the House.

"But they don't include the biased media; they don't include a bias and prejudice and deceitful members of the Opposition."

The National Party also has a foundation, but according to party president Peter Goodfellow, National discloses all donations over $15,000 to the foundation as though it were to the party.

At a number of times during Peters' speech, he clashed with Deputy Speaker Anne Tolley; at one point she forced him to apologies for implying that Smith had deliberately misled the House.

"Just follow the script, Madam Speaker. Even you should be able to do that," Peters snapped at Tolley at one point.

After Peters' speech, Smith attempted to table the letter from Lester Gray and Colin Forster.

Peters objected to the letter being tabled, so Smith distributed it himself.

Gray resigned in October, two weeks before the party convention, and according to Stuff, his resignation letter said he was unable to sign off the party accounts.

"I refuse to sign off the 2019 Financial Reports with the information I have been provided," he wrote.

"As President, the limited exposure I have had to Party donations and expenditure leaves me in a vulnerable position.

"This type of operation does not align with my moral and business practice values, and I am therefore not able to support the Party any longer."