A total of 28 present MPs qualify for a 90 per cent taxpayer-funded discount for overseas travel, including private holidays.

Act's Sir Roger Douglas and Labour's Chris Carter bore much of the publicity as big-spenders after the Parliamentary Service opened the books for the first time this week on individual MPs' spending on travel and accommodation costs.

But those elected at the 1996 election or earlier get the same discounts. A further 13 MPs qualify for a 75 per cent discount - those elected in 1999.

MPs qualify for a 25 per cent subsidy on overseas travel after serving one term, a 50 per cent after two terms.

In all cases, the MP's spouse qualifies for the same taxpayer-funded discount.

Unlike former MPs, who get the equivalent of a free return business-class trip to London each year for them and their spouse, there is no limit to the total amount of subsidy a qualifying present MP can claim each year.

But the actual amount spent by MPs each year - either individually or in total - on the subsidy for international travel remains a secret.

On Thursday, Speaker Lockwood Smith released figures for all air travel by MPs but there is no breakdown for international or domestic travel.

The fact that MPs refuse to have the Official Information Act applying to parliamentary spending, as opposed to ministerial spending, means two sets of standards of accountability apply.

Mr Carter, when he was a minister, was obliged to supply details of his travel including the cost and purpose, when asked - and then as now he was always a big-spending traveller.

But for travel subsidies paid by Parliamentary Service, they have to disclose nothing - not the reason and not the cost.

Former National and New Zealand First MP Michael Laws said it was a "complete rort" and a "dirty system".

You could not tell whether it was to attend the Bledisloe Cup or go on a shopping expedition, he said. "We are not in a position to know if we are being ripped off."

Mr Carter, Labour's foreign affairs spokesman, refused to comment yesterday on his travel but a party spokesman said a trip to China, Britain, the United States and Canada had been part work and part personal.

MPs and their partners have unlimited domestic travel.

90 per cent for MPs with 12 or more years' service:

Bill English
Gerry Brownlee
Nick Smith
Tony Ryall
Maurice Williamson
David Carter
Murray McCully
Lockwood Smith
Wayne Mapp
Georgina te Heuheu
Eric Roy
Chris Carter
Phil Goff
Lianne Dalziel
Ruth Dyson
George Hawkins
Pete Hodgson
Annette King
Nanaia Mahuta
Trevor Mallard
Damien O'Connor
Ross Robertson
Rick Barker
Jeanette Fitzsimons
Tariana Turia
Roger Douglas
Rodney Hide
Jim Anderton

75 per cent for MPs with nine to 11 years' service:

Simon Power
Lindsay Tisch
Pansy Wong
Phil Heatley
Paul Hutchison
Steve Chadwick
Clayton Cosgrove
David Cunliffe
Parekura Horomia
Mita Ririnui
Sue Bradford
Keith Locke
Sue Kedgley