Labour is questioning whether National Party leader John Key put a misleading or false address on documents relating to his electorate or his companies.
The attack, mounted in Parliament yesterday by Health Minister Pete Hodgson, is being dismissed as "desperate" by Mr Key who says he has a legal opinion stating he has done nothing wrong.
Mr Key has been the subject of Labour barbs several times this month, particularly on his stance about the Iraq war.
Yesterday it zeroed in on Mr Key's return under the Electoral Act nearly five years ago and returns to the Companies Office around the same time. The issue has been raised before by Labour but it claimed some of the details were fresh.
Mr Hodgson said Mr Key had put different residential addresses on the documents, and effectively accused him of making a false or misleading return to the Companies Office.
"Someone's getting told a porky here," Mr Hodgson said.
Mr Hodgson's office later circulated details of Mr Key's various returns, which showed an address in Remuera in March 2002, in Helensville in November 2002, and Remuera again in April 2003.
"When he told the Companies Office in 2003 that he was living in Remuera was that in fact correct?" Mr Hodgson asked.
"Because he'd told the Chief Electorate officer a few months earlier that he was living in Helensville."
Mr Hodgson later told the Herald that he was not sure whether Mr Key had broken any law, and in fact it was "entirely possible he hasn't".
Asked why the issue had been raised now, Mr Hodgson referred to a recent Herald article which discussed how many MPs lived outside their electorates.
He said that had triggered some interest, the Labour Party had already done some "digging", and he collated it and took it to the House for the general debate.
He also referred to the poll ratings of Mr Key, and said the type of scrutiny he was subjecting the National leader to was what happened to any politician who looked like he might be a candidate for the job of Prime Minister.
Mr Hodgson's attack met with immediate derision from National Party deputy leader Bill English, who said that on a day when New Zealanders were thinking about high interest rates, events in the global economy and the state of the health system, the most important thing was apparently where Mr Key lived in 2002.
Mr Key later said the Electoral Act and the Companies Act were different pieces of legislation and did not have to comply with one another. He said it hadn't been possible to register himself to his Parnell house in 2002 because it was a building site.
His Orakei home was not going to be a long-term home and the intention was to spend a lot of time in Helensville. "As it turned out I never really did," he said.
Mr Key had sought an opinion from the Clerk of the House and has a letter in reply which states the companies legislation did not affect his registration for electoral purposes.
The letter also states that under the Electoral Act a person can reside at only one place, but a person can have a number of residences for Companies Act purposes.
Mr Key also referred to legal advice he had which backed him.
"They're [Labour] just trying to smear me again," Mr Key said.