National Party chief whip Chris Tremain says there is no formal agreement with the Labour Party not to criticise MPs' expenses.
The expenses of MPs were made public for the first time on Thursday. The information details travel and accommodation spending for the first six months of the year.
Mr Tremain, who administers the expense claims of National MPs says releasing the information will allow for more comparison about MP spending.
But Mr Tremain, speaking on Morning Report on Friday, was reluctant to discuss whether any kind of a deal had been done between National and Labour.
He says disclosure of expenses is a good thing, but disagrees that Parliament should come under the Official Information Act to ensure full public disclosure of MPs' spending.
MPs have all but closed ranks over the expenses disclosure, resisting political point-scoring on the matter because it could put at risk their current entitlements.
Senior Labour Party MP Trevor Mallard says he will not criticise any MP's expenses.
Mr Mallard denies there was any informal arrangement, but says he did meet Mr Tremain by chance on Thursday, after he had received the figures.
He says he made it clear to Mr Tremain that he would not attack individual MPs for their spending.
Parliament released details of MPs' spending after an expense claims scandal in Britain prompted politicians in New Zealand to open up their spending to public scrutiny.
Speaker of the House Lockwood Smith says the figures have been released in the interests of transparency, but adds that they should be considered in the context of where MPs live and the demands placed on them by their constituents.
No transparency - Laws
There is still a scandalous lack of transparency about MPs' expenses despite the release of spending details, says Wanganui Mayor and former MP Michael Laws.
Mr Laws says it is impossible to know where MPs have been travelling to and whether it is for business or pleasure.
Mr Laws says that, in his time as a National and NZ First MP, people administering the system told him to treat travel as a perk of the job in exchange for a bigger salary.
He says the system will not be sufficiently transparent until the Official Information Act applies to all of Parliament, including Parliamentary Service, which administers Parliament's operation.
Foreign Affairs Minister Murray McCully is the biggest spender, at $353,000 for the first six months of the year.
Labour's foreign affairs spokesperson Chris Carter had the highest travel expenses of any MP not a minister or party leader.
Mr Mallard says Mr Carter has a responsibility to travel overseas to represent the Opposition, and he is not questioning Mr McCully's expenses either.
The details made public on Thursday show that MPs spent on average nearly $40,000 - excluding GST and fringe benefit tax - in the six-month period, though many MPs spent considerably less than $30,000.
Cabinet ministers and Opposition leader Phil Goff had the biggest bills.
Douglas defends, Carter complains
ACT MP Sir Roger Douglas has defended spending $44,000 on air travel in the first six months of the year.
Sir Roger, who has himself repeatedly criticised excessive government spending, explained the high cost by saying that he and his wife had flown to London on a taxpayer-subsidised trip, during which he spent some time with his son and grandchildren.
ACT leader Rodney Hide, who once campaigned against MPs' perks, also defended Sir Roger's use of taxpayer-subsidised travel.
Mr Carter, who spent $57,000, rang Radio New Zealand on Thursday to complain when his spending was reported, but declined to talk on the record. It was left to Mr Mallard to defend Mr Carter's spending.
Big claims by Maori MPs with big electorates
Maori Party MPs - excluding their ministers - claimed an average of $55,000, but the very big Maori electorates by definition cost more to properly service.
MPs from large rural general electorates have also made higher claims.
Revised figures will be issued every three months.