A political commentator believes Phil Heatley has fallen on his sword with the best intentions.

The Whangarei MP has quit his cabinet duties over a $70 ministerial claim mistake, for two bottles of wine. His spending over the past 18 months is now under scrutiny by the Auditor-General.

Richard Griffin says although it seems a little over the top, Mr Heatley takes himself very seriously and prides himself on his high morals. He says it appears to be a real crisis of conscience.

Mr Griffin says the inexperience of Mr Heatley's staff played a role in the faux pas. He says in the past, ministers have relied on their staff to keep an eye on when and why their cards are used, but with John Key allowing MPs to appoint staff who have not been to the Beehive before, they generally do not know the processes.

Mr Griffin says an experienced staffer would have cleared up the mess long before it hit the headlines.

However, the question around Parliament is did the Whangarei MP jump because there might be more mistakes on his claims. Labour deputy leader Annette King believes more answers are needed. She says it is strange a minister would stand down when the Prime Minister said he did not need to.

Mr Heatley's immediate political future now rests with the Auditor-General. Lyn Provost is investigating whether he has any more explaining to do over the use of his ministerial credit card.

John Key has left the door open for him to return to Cabinet if Lyn Provost's inquiry finds no further problems. The Prime Minister says he will make a decision on Mr Heatley's future once he has seen the Auditor General's report.