The Prime Minister's dismissive attitude towards concerns about New Zealand being seen as a tax haven is partly due to his links to the foreign trust sector, the Labour Party says.
In a 2014 email, Prime Minister John Key's personal lawyer Ken Whitney said he was worried about what Inland Revenue (IRD) might be planning and lobbied Mr Key against any changes to the foreign trust regime.
Despite expressing concerns about the reputational damage to New Zealand, the IRD decided last year that no review would be held.
Foreign trusts, and New Zealand's rules, have been under the spotlight since the release of the so-called Panama Papers in early April.
The leaked documents revealed how Panamanian law firm Mossack Fonseca orchestrated a worldwide web of companies designed to let people hide money and dodge taxes.
Labour finance spokesperson Grant Robertson said Mr Whitney got privileged access to the Revenue Minister to lobby against changes to the foreign trust laws.
"Look, I think New Zealanders are getting sick of the half-truths from John Key on this," he said.
"He hasn't been upfront about the extent of his contact with his lawyer, and the fact that his lawyer is so deeply involved in the foreign trust industry."
Mr Robertson said an independent inquiry was needed to restore New Zealand's reputation as a fair and corruption-free country.
Mr Key said he personally had no involvement in the decision by IRD to not carry out a foreign trust regime review.