MPs' expense accounts are likely to be opened to public scrutiny after a face-saving move by Prime Minister John Key led to an urgent cross-party meeting being called.

Party representatives will meet this week to discuss ways of giving more details on how MPs use their $14,800 expense accounts and accommodation and travel allowances.

The expenses are not detailed, and are not subject to the Official Information Act like other Government departments.

Both major parties had resisted changes until Mr Key called for the meeting yesterday.

When the question of MPs' expenses was raised three weeks ago, Mr Key said it was a matter for Speaker Lockwood Smith.

Dr Smith has also been reluctant to move to greater transparency, saying MPs "are under enough scrutiny as it is".

But he quickly heeded Mr Key's call yesterday, saying he would convene the meeting "as soon as practicable", probably this week.

The turnaround came after the Green Party promised to disclose its MPs' expenses spending each year. Act and the Maori Party followed suit.

The focus on expenses follows the furore in Britain after expenses claimed by House of Commons MPs were exposed as covering items including moat cleaning and duck houses.

Mr Key said the fallout from the British scandal could not be ignored.

"We can't sit back and be blind to the fact that what happened in the United Kingdom has increased pressure from voters around the world for a higher level of transparency."

National would support the cross-party committee's recommendation, which could result in Parliamentary Services - the department handling MPs' expenses - made subject to the Official Information Act like all other Government departments.

There was a "lot of history" behind Parliamentary Services exemption, but Mr Key said this was "clearly evolving".

His concerns were accessibility to MPs' phone records and the travel of MPs being taken out of context.

"Someone who lives in Otaki doesn't have an air flight bill like [National MP] Eric Roy in Invercargill."

Labour leader Phil Goff said the New Zealand system was robust: "I can't claim for a moat."

Dr Smith said several questions relating to the extent of disclosure would have to be considered, including the need to ensure that the privacy of MPs' constituent work was not compromised.

The New Zealand system did not provide for many of the claims that had caused concern in Britain, but "it is in the public interest to assure the integrity of our system".

Greens co-leader Metiria Turei said the New Zealand system was more robust than Britain's, but more openness was needed.

The proposed committee was a delaying tactic, she said.

"We'll engage with the committee - we think it's good that there is a systemic way of managing MPs' expenses and there should be standardised reporting.

"We also think the parliamentary services should be open to the Official Information Act, barring communications between MPs and their constituents."

Act leader Rodney Hide said he was happy to have his expenses made public.

Act would be part of the committee, but committees were a "kick to touch".

"I think we should just open it up to the OIA like everything else that's to do with public money."

Ms Turei invited other parties to join the Greens and Act in revealing expenses details.

But Labour whip Darren Hughes rejected the invitation, and Mr Key said it was up to individual MPs to decide.

* What MPS get

A basic annual salary of $131,000. Those with extra responsibilities, such as party leaders and ministers, are paid more.$14,800 a year allowance, in fortnightly payments with salary, for "parliamentary purposes". These include entertaining staff and constituents, koha and gifts. MPs are not required to produce supporting receipts.

Up to $24,000 for accommodation costs while in Wellington but only if they primarily live outside the capital. A maximum $160 for a night in a hotel, and $50 a night for a private arrangement, such as at a friend's house. Up to $480 a week to rent a property. If they own a house, $24,000 can be claimed against the interest of a mortgage.

Unlimited free domestic air travel, extended to a spouse or partner.

Up to 90 per cent of private international air travel.

MPs' children get four return trips to Wellington. Under-fives have unlimited trips.

Unlimited taxi use for "parliamentary purposes". A spouse or partner is also allowed certain rides.

Rental cars or mileage paid for personal car when on "parliamentary business".

Travel by rail, ferry or bus between New Zealand cities. Spouse or partner included.

Security system installation up to $400. Annual monitoring costs of $600.

Up to four landline rentals. High-speed internet at office and home. Phone card for "parliamentary business".

Cellphone and a hands-free kit for car.

Superannuation subsidy of $2.50 for every dollar the MP puts in. Can put in up to 20 per cent of salary. Longer-serving MPs are on a more generous scheme.

MPs who become ministers get further entitlements, such as a house in Wellington.