A global ratings agency is warning the number of Australian households falling behind on their mortgage repayments has hit a record high.

Fitch Ratings says the number of borrowers falling behind on repayments by 30 days or more climbed from about 1.4 per cent to 1.79 per cent in the first quarter.

However it is a delinquency rate that would be envied by European or American authorities, where the rate is four times and 20 times higher respectively, but for Australia it is the worst on record.

The ratings agency blames one-off factors like the Queensland floods and other natural disasters and says rising interest rates mean delinquencies are likely to worsen.

The group's associate director, James Zanesi, says the situation for Australian borrowers is becoming worrying and any flow-on effect from a rise in interest rates will take time to be seen.

"Even if the Reserve Bank of Australia is increasing interest rates in June it will take a couple of months for borrowers to be impacted by an increase of interest rates," he said.

"It's true actually that the situation for borrowers is becoming a bit worrying, but it is not still... as bad as, for example, other mortgage markets like the UK or in US."

Mr Zanesi says the first quarter of the year is normally a bad one for repayments because people have splurged on Christmas and holidays.

But he says this year is especially bad because of the effects of the floods in Queensland and Victorian, and Cyclone Yasi.

Last week ratings agency Moody's downgraded the debt ratings of the Australian banking sector and brokers Goldman Sachs have cut their view of some Australian banking stocks, which have dived over the past month as global investors have sold out.

But Mr Zanesi says Fitch still takes a positive view of Australian banks.

"Arrears are still very low, but definitely the Reserve Bank of Australia should take into consideration these among other factors and then make the appropriate decision," he said.

'Resilient borrowers'

In an address to stockbrokers this morning, the deputy governor of the Reserve Bank, Ric Battellino, defended the mortgage situation in Australia, saying borrowers are resilient and arrears rates are low by international standards.

"Contributing to this better outcome in Australia was the fact that the deterioration in lending standards was not as severe or as widespread as in other countries," he said.

Mr Battellino says Australians are now more cautious at borrowing than in the past 15 years when households became increasingly in debt.

He says households are now borrowing at a slower rate and saving more.

That is something the Reserve Bank welcomes, but Mr Battellino says there are pockets of stress and many first home owners lured into the market by the boost to the first home owners grant in 2009 bear watching.

"The concern is that some of these at least may have over committed themselves financially in order to enter the market and are now vulnerable to rising interest rates," he said.

"This group bears close watching but so far at least, first home owners do not seem to be disproportionably represented in loan arrears."

The Reserve Bank is expected to lift interest rates again before the end of the year.