For its own sake - if for no other reason - Labour must demote Shane Jones. Moreover, Labour knows it must.

So far, punishment of the former minister has not stretched beyond a severe ticking-off down the phone-line from a furious Phil Goff who is out of the country.

Goff well understands that stern words alone are not enough to reassure the public that Labour is genuine in its condemnation of the misuse of taxpayer-funded credit cards by its ministers during its time in government.

The Labour leader will be taking soundings before next Tuesday's caucus meeting, at which Jones is expected to get a roasting for billing taxpayers for the pornographic movies he watched in hotel rooms.

The Labour leadership has ruled out Jones' resignation from Parliament and says his political career can be resurrected if, in deputy leader Annette King's words, "he keeps his head down and bottom up".

Resignation would be too harsh a punishment and anyway carries the risk that the MP will not oblige.

In addition, the unwanted Judith Tizard - who incidentally used her ministerial credit card to buy a $155 bottle of Bollinger champagne - is next in line to come into Parliament off the party list.

Goff will instead be considering other options such as demoting Jones from Labour's front bench to send the right message to the electorate - not least because he insisted Housing Minister Phil Heatley did the correct thing in resigning from the Cabinet for putting two bottles of wine on his ministerial card.

Heatley's indiscretion now looks like small beer compared to Jones' serial misuse of his card.

The problem is that singling out Jones, Labour's 11th-ranked MP, for punishment will beg the question of why Chris Carter, who is ranked No 7, has escaped punishment despite unauthorised use of his card.

Goff will be cognisant of the need to be consistent. He could even mete out punishment to both those MPs by bringing forward a much-needed reshuffle of Labour's shadow portfolios.

But he will also have to be careful to avoid accusations that he is taking advantage of Jones' humiliation to deal to a potential threat to his leadership.

On that front, however, Jones has done his chips for a very long time. It is not only that he has embarrassed the party. As someone who sits on the right of the caucus, exposure of his consumption of pornography makes it well nigh impossible for him to build bridges with those more to the left.

More fundamentally, however, his behaviour will raise questions in his colleagues' minds about his judgment. That particularly applies to the way in which he has handled something he knew would be hugely embarrassing for him and the party.

Before yesterday's humiliation, he had tried to front-foot his credit card spending in the media, but consistently failed to be upfront about what he had spent the money on.

His credibility is consequently completely shot. His demise reinforces Goff's grip on the leadership. All of which is good news for National. Not that National was crowing about that. Some of its ministers - notably Tim Groser and a mini-bar bill containing numerous mentions of The Famous Grouse whisky - also had some explaining to do.

On a day when human foibles were so nakedly exposed, so to speak, there wasn't much for anyone to cheer about.