UPDATED: 11.53AM Britain's opposition - having forced a statement from the Prime Minister on his personal wealth in relation to the Panama Papers - is after more blood.

David Cameron has taken the unusual step of publishing his tax records to try to end days of questions about his late father's offshore fund.

SNP MP Angus Robertson wants the whole cabinet and members of the Chancellor's team of Treasury ministers, to make similar declarations.

"We have heard absolutely nothing about other members of the Cabinet. Where is the Chancellor of the Exchequer George Osbourne? Has he made a declaration that he has never ever benefited from off-shore trusts?"

Former Conservative Party politician Iain Dale told Mike Hosking the Panama Papers saga could lurk for some time.

LISTEN ABOVE: Iain Dale talks to Mike Hosking

"[Cameron]'s making a statement to Parliament tomorrow, but there is this sort of anti-corruption summit in London at the beginning of May, so it's not a story that's going to disappear altogether.

"The fact of the matter is [Cameron] didn't lie, he paid all of his tax and he's done nothing illegal. Although the Labour party has done quite well at keeping this story going I think for most people, it's a bit of storm in a teacup."

Meanwhile, John Key's sounding uncomfortable over the Panama Papers dump when it comes to New Zealand's role as a tax haven.

He's gone from denying anything's an issue last week... to hedging when pushed by Mike Hosking today

"The advice we get is that New Zealand has full disclosure, it has a good regime and it's doing things professionally. But if there are changes that need to be made, Government will make them."

There have been calls for the government to hold an inquiry into New Zealand's role.

Those have been rebuffed... until this morning.

Key now told Mike Hosking today the Government is going to get an internationally recognised expert.

"Someone with great credentials to go away and look at the disclosure rules in New Zealand. Make sure we're ticking all the boxes."

Key was asked why -- as a money man -- he didn't understand these things better.

"Well I'm not a technical experts in trusts but I know enough. But the point is we just accept the advice that we get and if the advice is we need to change more, we will."

Labour leader Andrew Little said one man carrying out tax checks behind closed doors doesn't provide enough transparency on New Zealand's involvement with the Panama papers.

Little said a full, open enquiry, with details made available to the public, is required.

"We also need to know which New Zealanders or New Zealand companies are affected or tied up in this and then we need to be sure our public officials too, including the Prime Minister, are squeaky clean on these foreign tax trusts."

Labour Leader Andrew Little says given the number of world leaders who've been implicated, it's not unfair to ask John Key to be absolutely crystal clear about his investments.

He said it's not enough for Mr Key to admit he has an overseas superannuation fund, that's not the issue.

He said New Zealanders want to know if he's ever used or benefited from a foreign trust that avoids taxes.

Malta is the latest country to call on two senior Cabinet ministers to quit over their financial arrangements.

One of them, Health and Energy Minister Konrad Mizzi, set up a company in Panama and has a trust in New Zealand.