(Adds detail, background on previous figures.)
STOCKHOLM May 7 Borrowing among households with mortgages and other debts in Sweden is greater than previous estimates of aggregate household debt levels indicate, a central bank study showed on Wednesday.
The Riksbank has been worried about high levels of household debt and has kept monetary policy relatively tight despite very low inflation, to curtail more borrowing.
The study of data from Sweden's eight biggest banks by the Riksbank underlined the risks from borrowing.
"Swedish household debt in relation to disposable income is higher than previous studies have shown," a Riksbank statement said. "Swedish households' debts have grown substantially in recent years and the Riksbank has emphasized, in various contexts, the risk this entails for both macroeconomic development and financial stability."
Stripping out families with no debt from the figures, the Riksbank said that household debt was 313 percent of disposable income for households with mortgages and 263 percent for households without mortgages.
The Riksbank also said that four out of ten borrowers are not reducing their debts - and those who are reducing them are doing so very slowly.
The Riksbank has previously referred to an aggregate figure that combined households with debt and those without. Even using that figure - now around 174 percent of disposable income - Swedish borrowing is some of the highest in Europe, leading to fears that any decline in property prices could have a big effect on overall demand and worsen any future downturn.
Sweden has taken several measures to cool its housing market. The financial watchdog introduced a cap on mortgage borrowing of 85 percent of the purchase price of a home in 2010.
Mortgage risk weights - which determine how much capital a bank must set aside for mortgages - have been raised to 25 percent from around five percent of risk-weighted assets.
However, central bank Governor Stefan Ingves has called for more measures to be taken to head off any threat to economic stability.
(Reporting by Daniel Dickson, Simon Johnson and Johan Ahlander; Editing by Larry King)