Bernard Hickey: Killjoy's the only adult in the room

There are real risks to financial stability if an over-valued housing market goes bust. Photo / File

Who will help the grown-up?

Every parent knows there's always a moment at a party when the 5-year-old has had enough chocolate cake, or the 18-year-old has had enough vodka and Red Bull.

Saying no to pleas for "more, more" is what a responsible adult does. That adult knows everyone will be better off in the morning.

New Zealand's economy is at that point in the party.

In the 1950s former US Federal Reserve chairman William McChesney Martin coined the phrase that it was the central bank's job to "take away the punchbowl just as the party gets going", by lifting interest rates to slow inflation. Back then people actually drank punch and inflation did spike.

Now it's time for New Zealand's grown-ups to take the alcopops from home buyers before they wreck the joint and give themselves and the economy an almighty hangover.

There may not be the inflation pressures of the 1950s, 60s and 70s, but there are real risks to financial stability if an over-valued housing market goes bust.

Reserve Bank Governor Graeme Wheeler spent most of the past decade in America watching just such a housing bust and the financial carnage that followed. That's why he is now collecting the unopened cans and turning on the lights to slow rampant low deposit mortgage lending.

Thank goodness, because it seems as if all the other grown-ups have lost their senses.

Prime Minister John Key made a last-ditch attempt to keep the party going by asking Wheeler to give first-home buyers an exemption, which seems to have failed.

The disappointing news this week was both Labour and the Greens also called for the Reserve Bank to exempt first-home buyers. They couldn't resist using the situation to try to score political points off Key, saying he had handed a loaded gun to Wheeler by allowing the bank to create a macro-prudential toolkit that didn't exempt first-home buyers. They couldn't resist the easy appeal to the kids to keep drinking.

Just when the Reserve Bank needed support to avoid the financial fallout of a possible bust, National, Labour and Greens took the cheap, easy and "cool" option.

They acted like middle-aged parents, wanting their teenagers to think they were cool by turning up the music and showing off their best More FM dance moves from the 70s, 80s and 90s. It's never a good look.

Any political party that really wants to look after the best interests of first-home buyers shouldn't be encouraging them to gear up with cheap debt. Those first-home buyers who have never experienced a sharp rise in interest rates or a fall in house prices will wish in years to come that someone had been the grown-up at the party.

The sole grown-up in the room needs help to turn off the stereo, not an unseemly display from half-cut 50-year-olds wanting to jiggle the night away.