Labour MP Chris Carter believes he has received more attention over his travel costs and spousal travel because he is gay, implying the news media have a prurient interest in him.

"Why was there no interest in any other minister taking their partner with them, only me? Why should that be?" he said yesterday.

"The only conclusion that I can draw from that is it's because I'm gay, and that if I was a heterosexual minister taking my husband or wife with me, it would be of no interest."

Mr Carter also denied that his high travel costs had been drawn to his attention by Labour colleagues, contrary to Herald sources.

"It is simply not true. No colleague has ever said that to me to my face," he said.

Mr Carter has said that his spouse, Peter Kaiser, often accompanied him.

He said that as Education Minister he had been only the fourth-highest travelling minister last year - behind Foreign Minister Winston Peters, Prime Minister Helen Clark and Trade Minister Phil Goff. All of Mr Carter's eight trips as a minister were approved by the Prime Minister.

The costs of ministerial travel, funded by Ministerial Services, have been published frequently under the Official Information Act, and the latest figures were 10 days ago with new disclosures of spending by all MPs, as MPs, funded by Parliamentary Service.

Mr Carter said he would not be disclosing that figure, but it would not be high because he was so busy as a minister he rarely took holidays. He might have taken one last year.

Parliament's Speaker, Lockwood Smith, yesterday reiterated his intention not to release figures showing the expenditure of MPs on private overseas travel, using between a 25 per cent and 95 per cent discount.

On TV's Q and A yesterday, he initially told Paul Holmes that the public would be able to see the figures, but then said they would not be released and people would be able to work it out from those MPs whose travel expenses were "extraordinarily high".

Air travel for MPs is classed as one figure, and international is not separated from domestic.

When Holmes challenged Dr Smith over the extent that spouses travel with MPs, Dr Smith challenged him to stand for Parliament.

"There have been quite a few in the media who have, over recent times, and they've bailed out real fast when they've found actually the going was a damn sight tougher than they expected."

Green Party co-leader Metiria Turei told the Herald she supported not just a review into ministerial housing that Prime Minister John Key ordered last week, but into all MPs' expenses.

She believed it should be conducted by someone who knew the job, but not by present MPs.

She believed the subsidy for overseas travel - for MPs' travel, not ministerial travel - should apply to sitting MPs, not former MPs only, and that it should apply only for work-related travel.

At present it could be used for any purpose, holiday or work-related.