Chris Carter says his travel expenses were focused on because of his sexuality.

Mr Carter today announced he would be quitting politics and had withdrawn his nomination for his Te Atatu seat following an uproar over an anonymous letter he said criticising Mr Goff's leadership.

Mr Carter told NZPA today he was hurt by criticism of excessive spending on travel while a minister and Mr Goff was in Cabinet when his travel spending was approved and it was all work related.

In an interview with GayNZ.Com, Mr Carter said the way attention focussed on his travel with partner Peter Kaiser was about the fact they are gay.

"I spent 15 years as an MP, six years as a Cabinet Minister, working my guts out really. And to have this stuff with my partner constantly on television and named, his school named where he's principal. Who's ever heard of another MP or minister's partner ever being dragged into it like this?

"To have Phil Goff say it's not homophobic - of course it's homophobic. Why was I different to everybody else? Because I was the top spending MP? I wasn't actually. Because I was the top spending minister? I was number four actually. And I was the Education Minister. Of course I had to be. International students are our fourth largest overseas earner."

He said not all his gay colleagues had been supportive.

"Charles Chauvel's been great. But I'd prefer not to speak ill of the others, but they have not been supportive. That was really difficult to deal with as well. But you know, I don't want to sound bitter, nasty or unhappy."