If Trevor Mallard seems a trifle under-unemployed since last week's Labour reshuffle, it has given him even more time to indulge in what Speaker Lockwood Smith calls "mischievous behaviour".

In yesterday's case, however, most MPs would have deemed Mallard's witty contribution to have been a harmless bit of fun.

A clever play on words had him land a reasonable hit on John Key during Parliament's first question-time of the year.

Instead of starting his question to Key in conventional fashion with the words "Prime Minister", Mallard referred to National's leader as the "Prime Mincer" - a reference to Key's mincing down the catwalk and camping it up during last week's unveiling of Rugby World Cup volunteers' uniforms.

Mallard's little joke provoked laughter on all sides of the House. Even his victim managed a grin before quickly recovering.

"Can I say to the member that I appreciate the fact that he has his hair very similar to mine - undyed and quite short, and grey on the sides," the Prime Minister responded, making the inevitable dig at Labour leader Phil Goff.

Key had been having fun himself tormenting David Parker, another Labour front-bencher, over Labour's opposition to partial state asset sales. Given that opposition, Labour not surprisingly used question-time to quiz the Prime Minister on the likelihood of shares in state-owned enterprises like Meridian Energy falling into foreign ownership. Labour also challenged Key on whether many New Zealanders could afford to buy shares.

Key, however, wanted to know why Clayton Cosgrove was asking Labour's questions when Parker, who is Labour's new energy spokesman, had told his local paper he would be the one leading Labour's campaign opposing the partial sale of state electricity assets.

"Can I just say how surprised I am that the member is asking me that question, because David Parker was reported in the Otago Daily Times yesterday saying that he would lead the charge on state-owned enterprises."

If Cosgrove was asking the questions, it was for a very good reason. He is Labour's spokesman on SOEs, not Parker.

Key really started to enjoy himself as other Labour MPs rose to their feet to ask him supplementary questions, while a now sheepish-looking Parker stayed affixed to his seat.

When Labour backbencher Kelvin Davis - ranked 27th in his party's caucus to Parker's fourth - got the call, Key pleaded with him "to have the decency" to pass his supplementary question to Parker.

At this point, Mallard came to Parker's rescue with his "Prime Mincer" quip - an intervention which earned him an instant rebuke from the Speaker. "The member knows he cannot do that. He has just lost his supplementary question."

But it was not for long. The Speaker was soon expressing his annoyance with the Prime Minister for comparing hairstyles and colouring with Mallard's.

"I have allowed too much misbehaviour today ... I penalised the Hon Trevor Mallard for a very disorderly comment, and I do not think the Prime Minister's comment at the end of that question was helpful. Labour has just regained its supplementary question."

In fact, the first question-time of election year was surprisingly good-natured and not especially raucous.

As to which party triumphed, the only conceivable verdict was a draw.