Reserve Bank governor Glenn Stevens says he is "very concerned" about Sydney's property market, parts of which he has described as "crazy".

Addressing a business lunch in Brisbane, Mr Stevens said the RBA was prepared to cut the cash rate again if needed, adding that it will be "quite some time before we even think about interest rates going up".

But he said Sydney's property price boom was "acutely concerning", even though most other capital city property markets were not rising strongly.

"I am very concerned about Sydney, I think some of what's happening is crazy, but we've got a national focus to manage as well - that just increases the complexity," he said.

"On whether or not that stays any hands [on interest rates], I have no comment."

The Reserve Bank governor's comments echo the warning of a property "bubble" by federal Treasury secretary John Fraser last week.

Speaking at a separate function in Sydney, ANZ chief executive Mike Smith denied the city was in a bubble, but said it is worth close attention.

"I don't think it's quite a bubble yet, but it certainly has the potential," he said.

On the affordability issue, Mr Smith said "buying your first house is always a stretch", and he pointed out that residents in some other cities overseas are in a worse position.

"I was speaking to an investor the other day who was saying, 'well house prices are getting higher in Sydney but, compared to Hong Kong and compared to New York, you're actually still considered quite good value internationally for the money'," he added.

Mr Stevens said booms funded by strong credit growth and poor lending standards were the most concerning, which is why the bank regulator APRA had taken action.

"We're trying to make sure that lending standards are maintained and indeed improved," he said.

"I think Wayne's [APRA chairman Wayne Byres] speech the other day showed areas of concern there, and a need not just for a maintenance of lending standards but an improvement."

He also warned that low rates and more borrowing can only do so much to boost growth.

Mr Stevens explained that households already had a lot of debt and cannot really afford to borrow more.

"Of all the three broad sectors – households, government and corporations – it is households that probably have the least scope to expand their balance sheets to drive spending," Mr Stevens observed.

"That's because they already did that a decade or more ago. Their debt burden, while being well serviced and with low arrears rates, is already high."

The comments seem to contradict Treasurer Joe Hockey's calls last month for households and businesses to go out and borrow money to invest and spend.

Mr Stevens said very low interest rates can lead to big problems with few benefits.

"It is not that monetary policy is entirely powerless, but its marginal effect may be smaller, and the associated risks greater, the lower interest rates go from already very low levels," he added.