Prime Minister John Key is calling for a cross-party committee to examine ways of creating greater transparency of MPs expenses.

Mr Key said he would write to Speaker Lockwood Smith today suggesting the committee be established.

The move follows an announcement by Greens co-leader Metiria Turei that its MPs would release their expenses for January 1-April 30, and a commitment to do so every year.

The decision was prompted by a scandal over MPs' expenses in Britain, where daily reports and embarrassing headlines have detailed the way MPs have used the system to claim for dog food, light bulbs, work on their houses and porn movies.

In New Zealand, details of ministerial expenses are subject to the Official Information Act (OIA) although MPs' expenses are not.

Mr Key this morning said the OIA, and parliamentary questions, meant there was a high level of transparency.

"That said, on reflection, it may make sense for there to be a committee formed of MPs, one from every political party to look at this issue, look if there are ways for greater transparency and on that basis I intend to write to the Speaker today and suggest to him he might like to form that group," he said.

"It could simply be something like an extension of PSC (the Parliamentary Services Commission) but the concept would be a member from every single political party, sit around the table, talk about how there can be greater transparency."

MPs had legitimate concerns about such things as accessibility to their phone records but needed to put that into perspective as they could only claim for domestic air travel, taxis and accommodation, he said.

However, the public had to remember that some MPs expenses would be much higher because of where they lived; the MP for Wellington would obviously spend far less on air travel than that for Invercargill.

"So you wouldn't want a Member of Parliament to be besmirched by the fact that they might have a slightly higher flight bill or taxi record simply because they live further away," Mr Key said.

Ms Turei said the public were having to tighten their belts and it was "only right that MPs make known to the public how the scarce taxpayer funds are being used".

"We think that the public is entitled to know," she told Radio New Zealand.

The Greens hoped to release by Friday details of their MPs' expenses. They would include partner travel but not details of individual flights.

"In our view, it's the total cost that the public want to know about -- how much it costs for MPs to do their work, and we think that that's reasonable that they have that information," Ms Turei said.

"So we invite all the other political parties to follow suit and to release this information to the public."

But Labour whip Darren Hughes said his party would not join the Greens in releasing expenses.

"I think in terms of the work expenses we're talking about, where people seek reimbursement for items to do with doing their job on an actual and reasonable basis, we've got a system that is transparent in terms of how it all works," he told Radio New Zealand.

"We also have a system of making sure internally that those claims are checked to make sure that they're reasonable before they go through."

Maori Party co-leader Tariana Turia said simply releasing totals would not give the public any idea whether funds were being used in a fair or just way.

"If you take the Maori electorates, just as an example, I imagine that the bill for rental cars would be considerably higher than anybody else's, and so might air travel, given the size of their electorates," she said.

Act Party leader Rodney Hide has promised to disclose his expenses.

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