First-term Auckland councillor Cameron Brewer is not ruling out challenging Mayor Len Brown for the mayoralty in 2013 after making a big splash in his first eight months.

The Orakei councillor and National Party member said a challenge was "highly unlikely ... but you never rule anything out in politics".

Speculation is growing about Mr Brewer's political motives after he was the only councillor to vote last week against Mr Brown's first budget and rates increase of 3.94 per cent.

On Facebook, City Vision councillor Cathy Casey said: "If the rumours are true, Cameron Brewer is aiming for a tilt at the mayoralty next time round.

"To do that, he needs to continue to oppose Len (even when everyone else agrees) and he also needs to keep himself in the public eye."

Despite describing himself as a "first-term junior councillor", the 38-year-old is an experienced political operator, energetic, ambitious and media savvy.

He worked for former Prime Minister Dame Jenny Shipley, Auckland City Mayor John Banks, Act MP Rodney Hide and in National's parliamentary research unit. Before entering politics last year, he was the face of the Newmarket Business Association.

Mr Brewer, who last year promised to bring a fresh and energetic approach to local body politics for the next six, nine or 12 years, said his current focus was to be a senior player in a centre-right-led council in 2013.

Asked about voting against Mr Brown's budget when he had previously called for a 3.9 per cent rates rise and the right-leaning Citizens & Ratepayers ticket had supported it, Mr Brewer said he wanted to signal it was the "same old, same old" and a change was needed.

He said Mr Brown had done well to unite Auckland, but he had serious concerns that the mayor would not deliver the big promises of amalgamation, particularly making the city more business-friendly.

A spokeswoman for Mr Brown said the mayor was not worrying about the next election. He was focused instead on issues such as transport, rates and the economy.

The mayor himself said: "If you are going to be mayor, you need to promote a positive vision for Auckland, and that's what I have been doing."