The strong performance of National candidate Hekia Parata in the Mana byelection has boosted her chances of being promoted this week.

Prime Minister John Key is expected to make an announcement on the Cabinet vacancy that has resulted from the resignation of Women's Affairs and Ethnic Affairs Minister Pansy Wong.

Ms Parata, a former public policy and Treaty of Waitangi consultant, not only slashed Labour's majority, but performed well under pressure and ran a strong team.

Counting against her is that she is a first-term MP. Her promotion ahead of the class of 2005 could put some noses out of joint.

The leading contenders in that pack are Craig Foss, the MP for Tukituki and chairman of the finance and expenditure select committee, and Chris Tremain, MP for Napier and the chief Government whip.

Selwyn MP Amy Adams, in the same cohort as Ms Parata, is also tipped for future promotion in a commerce or economic role.

Mr Key could save a little money by appointing no one to the Cabinet and appointing another minister outside the Cabinet. He could make an even bigger saving by appointing no one at all and upsetting no one.

But that would suggest Mrs Wong's role was surplus to requirements in the first place.

Mr Key is not seen as a slave to "political correctness"; he is not oblivious to gender and identity issues in National's line-up either.

With Mrs Wong gone, just five of National's 22 ministers are women.

Mr Key has made it clear previously that Ms Parata is ministerial material.

The importance of the Mana byelection is that a promotion would be seen on the basis of talent, not tokenism - as it was with Mrs Wong.

The week before Mrs Wong's resignation - over breaching rules around the international travel perk - Mr Key said he did not intend having a reshuffle before the election next year.

That suggests he will want to keep the reshuffle forced upon him to a minimum.

There are already three National ministers outside the Cabinet - Internal Affairs Minister Nathan Guy, Building and Construction Minister Maurice Williamson and Civil Defence Minister John Carter - and the PM has the option of appointing one of them to the Cabinet.

But none of them warrants it.

Making one appointment outside of the Cabinet to take over Mrs Wong's two portfolios makes most sense, and of the contenders, Ms Parata's sphere of interest is best suited to the vacancies.