One of Auckland's biggest talking points is dividing in Auckland councillors in two.

Auckland mayor Len Brown wants to start construction of the City Rail Link next year, ahead of Government funding in 2020.

He'll make his case to councillors tomorrow.

Councillor Dick Quax says at the moment, many councillors and local board members aren't sure it's the best idea.

"They see a lot of money being tipped into the CRL well before the Government has made its financial commitment."

Mr Quax says he's also worried the link could cost a lot more than current estimates suggest.