* Number of mortgages over 90 days in arrears up 11 pct in Q3
* 8.1 pct of mortgages in arrears for more than 90 days
* Levels still within provisions under EU-IMF bailout
* Over 90 pct of negative equity borrowers not in arrears
DUBLIN, Nov 18 (Reuters) - The number of Irish mortgages in arrears for more than 90 days grew 11 percent in the third quarter, figures showed on Friday, highlighting growing strains on the country's banks and adding to pressure for the government to help struggling borrowers.
More than one in 10 Irish home loans are not being fully repaid and the situation is deteriorating as unemployment remains stubbornly high and house prices continue to fall.
Stress tests carried out as part of Ireland's EU-IMF bailout have bulked up Irish banks' balance sheets to deal with rising arrears, but a recent programme memorandum warned there was potential for higher-than-anticipated losses.
"This is a reflection of what is going on generally in the economy and there is no sign it's going to change any time soon," said Alan McQuaid, economist at Bloxham Stockbrokers. "There are too many consumers still under water."
The central bank said 99,346 mortgages were either in arrears or had been restructured at the end of September, representing some 13 percent of the total residential mortgage market and up from 95,158 mortgages at the end of June.
The number of mortgages more than 90 days in arrears was 62,970 at the end of September, an 11 percent increase from the end of June. That represented 8.1 percent of all mortgages, up from 7.2 percent at the end of the previous quarter.
Stress tests published last March that forced Irish banks into a 24 billion euro recapitalisation assumed that 6.7 percent of their combined mortgage book would never be paid back.
Ireland is "some significant distance" from breaching that level, said Austin Hughes, an economist with KBC Ireland.
The government has expressed hope that the recent quarter-percent cut in the European Central Bank's key interest rate may help some consumers, but two of Ireland's main banks have refused to pass on the cut to all customers.
"At the margin, that will have helped a few borrowers, but if you do the maths the upside from the ECB rate cut will be overshadowed by the hit to taxpayers from further austerity measures in December's budget," Hughes said.
In a separate research document also released on Friday and based on data from 87 billion euros of outstanding debt, Ireland's central bank said over 90 percent of negative equity borrowers were not in arrears at the end of 2010.
The bank said the average negative equity of a borrower without arrears was 67,768 euros while borrowers who are also in arrears have a higher negative equity average of 83,911 euros.
Of those households in arrears over 90-days arrears, some 40 percent have been in this position for a year or more.
It added that two-thirds of owner-occupier mortgaged households have an outstanding debt of less than 200,000 euros with 30 percent struggling with debts of between 200,000 and 500,000 euros.
The remainder, less than 4 percent, have an outstanding debt over 500,000 euros, the monetary authority said.