Labour leader Andrew Little has tabled his tax records in Parliament, but failed to convince Prime Minister John Key to follow suit.
Mr Little said the Prime Minister should make a full disclosure to back his statements that all of his tax affairs were above board.
He sought leave during Question Time this afternoon to table his tax forms for the last five years.
The records covered Mr Little's time as chief executive of the EPMU, where his income rose to $178,000, and his first three years in Parliament.
After tabling the documents, Labour MPs yelled across the House: "Show us yours, John."
Mr Key said he would not release his records, and reiterated that any rumours that he held assets in foreign trusts were false.
He also shot back, saying that Mr Little should be tabling his CV instead, "because he will be out looking for another job soon" - a reference to Mr Little and Labour's poor poll results.
The register of pecuniary interests, published today, confirmed that all of Mr Key's investments remained in a blind trust, the Aldgate Trust. He was also a beneficiary of the Key family trust.
The register also revealed, however, that Mr Key's lawyer was the head of a company which specialised in foreign trusts - an embarrassing disclosure in the middle of the Panama Papers debate.
In the House, Mr Key said there were many legitimate reasons for having a foreign trust in New Zealand.
The release of the Panama Papers last week has placed greater scrutiny on politicians' tax arrangements.
Iceland's Prime Minister Sigmundur David Gunnlaugsson resigned after the documents leaked from a Panama law firm which specialised in tax haven activity showed that he and his wife had set up a company in the British Virgin Islands.
British Prime Minister David Cameron on Sunday released information from his tax returns for the past six years, and in doing so said he had failed to properly handle questions about his inheritance from his father.
Mr Key said yesterday that his tax affairs were above board and that he had never put assets into a foreign trust.
to reporters at Parliament this morning, the Labour leader said it would be "unsurprising" if Mr Key had sought to minimise tax on his assets because of his financial background.
"He is our Prime Minister now. And he is dealing with an issue about tax and the morality of tax dodging. And I think ... to give New Zealanders an assurance that he is squeaky clean and above board he should be disclosing his tax records in just the same way that David Cameron has now agreed he is going to disclose his."
In response, Mr Key said he would not publicly release his own records. The Standing Orders Committee determined what interests MPs should disclose, and he complied with his obligations, he said. Any move to release tax records would be a "big step" and would not satisfy those who wanted greater transparency.
"It wouldn't solve the issues that people would want. They ultimately would want all sorts of other disclosures around trusts and other things."
After entering Parliament, Mr Key placed nearly all of his assets in a blind trust based in New Zealand.
While he had never asked questions about the trust, he said that he had "total confidence" that any related activity or investments were above board.
One of Mr Key's investments, a timeshare at a ski resort in Colorado, was not placed in the blind trust. The company which owned the ski resort was registered in Delaware - a state known for tax secrecy.
Mr Key said that because the investment was registered in his name it was too difficult to move into the trust. He added that the investment had little value because the development "didn't go that well".
The Government yesterday announced a review of New Zealand's rules for foreign trusts, led by tax expert John Shewan.
Opposition parties criticised the review, saying the terms of reference for the review were too narrow and that Mr Shewan was not a disinterested expert because of his background in tax practice.
Mr Key said trust law was complicated and it would be difficult to find an expert without exposure to tax practice in New Zealand.