Accounting for $29 billion annually, BoMaD is the nation's ninth-largest mortgage lender and a port of call for almost 4000 "kidults" every month, according to comparison site Finder.

While it's natural for parents and grandparents to offer what they can, housing specialist Martin North is not sure in this case it's always good thing.

His company, Digital Finance Analytics, conducts a rolling national household survey which has tracked the massive spike in BoMaD borrowing.

He says the average loan is a whopping $90,000 but that's not the real concern. It's the fact that adult children who borrow from parents are three-to-five times more likely to default on their mortgage within five years.

"I'm not saying it's wrong and I'm not saying we shouldn't do it, but what I am saying is we should do it with open eyes," Mr North said.

"The trouble is that those who have not had the discipline of saving over many years for a deposit can find that when they are given that seagull payment, they probably buy a bigger property than they should."

That means taking on a bigger mortgage than they should without having learned the discipline of managing their finances.

For mum and dad or grandma and grandpa, it often also means handing down equity from their own properties on the assumption real estate prices are going to keep climbing as they transition into retirement.

Meanwhile, banks have stopped asking so many questions about where people are getting money for deposits, Mr North said.

"Underwriting standards aren't necessarily highlighting some of these issues" and that's down to regulation, which is determined by government policy.

"It's short-termism and it is going to come back to bite the hand that feeds."

With the average first-time mortgage 15 per cent larger than a year ago and people more leveraged into property at a time when it's already expensive, the big structural risks are building.

"Mortgage rates might be low but incomes are going backwards in real terms," Mr North said.

"This is not good policy from a structural perspective, let alone a household or social perspective. The problem is we have no one who is willing to step up and take responsibility."

Regardless, the market frenzy continues unabated.

There were 2934 capital city homes set to go to auction this week, according to data analyser CoreLogic.

That's down only slightly on last week's 3016 auctions held, which happened to be the second busiest week for auctions of the year.

Melbourne is expecting 1302 properties to go under the hammer, Sydney 1207, with volumes also higher in Perth and Tasmania.

Finder's findings on the extent of mum and dad lending was based on a national survey of 1028 first home buyers.

Australian Associated Press