Labour MP Chris Carter is facing further demotion unless he can show more public contrition and humility, despite his assurances that his apology last week was genuine.

Labour leader Phil Goff hinted yesterday that the matter was not settled, and he expected Mr Carter to face media when he returned to Parliament.

Mr Carter continues to work in his Te Atatu electorate after being placed on indefinite leave following the fallout from the release of ministerial credit card spending.

He issued an unreserved written apology to the public last week for his travel expenses while overseas on government business, adding that he was "contrite" and "embarrassed".

He spoke to Mr Goff on Sunday and "I assured him my apology was genuine".

But Mr Goff took the unusual step yesterday of publicly questioning Mr Carter's contrition. While he accepted the apology, he was still unconvinced that Mr Carter had fully acknowledged public displeasure over his expenses.

"I'm not sure yet that he understands why a genuine apology is needed, and that taxpayers in New Zealand have the right to expect their money to be spent frugally and with reserve," Mr Goff said.

"I took the apology in writing to be a genuine one, but he needs to believe what he says. I don't know that yet.

"My judgment is he is better off working in his electorate and sorting out what he needs to sort out. I'll be having a discussion with Mr Carter later in the week and I'll make an announcement after that."

He said he expected Mr Carter to give interviews when he returned.

It is understood that Mr Goff will make a decision on Mr Carter's future based on how he handles his press conference on his return.

It was Mr Carter's refusal last week, against the advice of his colleagues, to apologise or answer questions from the media that angered Mr Goff and led him to sending Mr Carter home to think about his future.

Mr Goff would not be drawn yesterday on whether Mr Carter would retain the conservation portfolio or his ranking, preferring to leave his options open. Mr Carter was stripped of the foreign affairs portfolio and dropped from the front bench.

Mr Goff has said the issue was more about Mr Carter's excessive travel bill while a minister - signed off by the Cabinet and then-Prime Minister Helen Clark - than about his use of his ministerial credit card on personal items.

He said Phil Heatley's charges to his ministerial credit card were much worse.

The Auditor-General later cleared Mr Heatley because his actions were not deliberate and he was unclear of the rules. Mr Heatley was reinstated to the Cabinet.

Mr Carter said yesterday he had had support from his electorate, and the "huge majority of emails and calls to my local office have been positive".

Mr Goff said Mr Carter had not undermined his leadership by seeking advice from Helen Clark.

"People are entitled to take advice from friends.

"I hope that Mr Carter listens to that advice."