Wellington, June 14 NZPA - Labour leader Phil Goff will sack Shane Jones and Chris Carter over the credit card spending saga, Prime Minister John Key predicted today.

Mr Goff returned yesterday from a trip to China and was immediately involved in the scandal around the credit card spending of some of Labour's former ministers.

He was understood to have spoken to Mr Jones and Mr Carter, two of the main culprits, and was likely to announce his decisions around noon.

Mr Key said Mr Jones was a "real threat" to Mr Goff as the party's leader.

"In the end he's going to sack those former ministers today," Mr Key told TVNZ's Breakfast programme.

That was good for Mr Goff and bad for Mr Jones -- an expected contender for Labour's top role.

"I'm not sure he'll (Goff) look terribly strong, he'll just eliminate one of his biggest threats.

"I think Shane Jones would have been the guy, they've certainly been positioning Shane Jones as the attack dog to come in and be the strong voice."

While the Labour Party was likely to be upset at losing Mr Jones "I don't think they'll be too worried" about losing Mr Carter, Mr Key said.

"It'll give them a chance to have a reshuffle that they need to have."

Mr Jones political career was not over, but Mr Carter's was likely to be, Mr Key said.

He also believed Mr Goff had not handled the issue very well.

"I think it was fairly well known actually."

A third Labour MP, Mita Ririnui, could also be disciplined.

Mr Jones has taken most of the fallout because he used his ministerial credit card to pay for dozens of in-house pornographic movies at hotels when building and construction minister in the previous government.

But Mr Carter racked up huge bills when he went overseas on numerous trips, although he held largely domestic portfolios such as education.

Mr Ririnui bought a bike and a set of golf clubs with his card and paid back the money, but there are explicit rules against that.

Mr Goff's reshuffle of portfolio responsibilities could also give him a chance to promote some of the talented MPs who came in at the last election, such as Grant Robertson, Jacinda Ardern and Phil Twyford.

Mr Key said much of the spending that had been questioned was within the rules and ministers often paid for large groups.

"On the other side of the coin, putting golf clubs and porn movies on your credit card, no one thinks (that is ok)."