Financial counsellors throughout Australia have reported a spike in the number of borrowers facing mortgage stress.

During the last quarter of 2016, counsellors at the National Debt Helpline reported that phone calls from beleaguered borrowers jumped 12% on the previous year to an average of 11,079 per month. That’s double the rate of increase from the same period a year earlier.

“It's steadily out of control … I don't know of too many financial counselling services where demand doesn't exceed supply,” Fiona Guthrie, chief executive officer of Financial Counselling Australia, told the Australian Financial Review. The biggest increase in calls is from people suffering from mortgage stress. “There are [now] more people who have got mortgages that they can't afford to pay,” she said.

Other warning signs that indicate the walls are ready to close in on Aussie borrowers include increases in mortgage arrears, a spike in lenders’ bad debt provisions, and growing personal insolvencies.

Australia’s households are among the most indebted after taking on more than $1trn in mortgages amid a housing boom. That boom has since fizzled out in some parts of the country, but is still charging ahead in Sydney and Melbourne.

While many households are still capable of servicing their debts, a worsening of credit metrics has executives and analysts taking a more cautious tone. The downgrade in credit metrics will be a major factor in the Reserve Bank’s cash rate decisions this year, with Governor Philip Lowe placing financial stability at the forefront of monetary policy.

The concern from regulatory bodies is understandable: private debt has soared to 187% of income, from about 70% in the early 90s. In a November speech, Lowe said that while most households are still capable of managing their debts, many are closer to their borrowing capacity than they once were.

“There's so much household debt that a couple of rate hikes here would completely knock the wind out of the housing market, and a lot of people would be impacted by it,” said Gareth Aird, an economist at CBA. That’s partly why he thinks the Reserve Bank won’t lift rates until 2018, at the earliest.