* Home loan arrears plus 90 days 11.9 pct vs 11.5 pct in Q3
* Buy-to-let arrears rise to 18.9 pct in Q4 from 17.9 pct
* More permanent solutions seen, long-term arrears deepen
DUBLIN, March 7 (Reuters) - Problem home mortgages in Ireland grew in the fourth quarter of last year at the slowest rate since statistics began to be collected three years ago, the country's central bank said on Thursday.
Ireland's heavily recapitalised banks have booked big losses on bloated commercial property books but have struggled to get to grips with mortgage debt, seen by the central bank as the country's biggest domestic policy issue.
Over one in six Irish home loans worth a total of 24.7 billion euros were not being fully repaid at the end of last year and the proportion of those in arrears for more than 90 days rose to 11.9 percent.
That was up from a slightly revised 11.5 percent in the previous three months, but the pace at which households are sinking into the red appears to be slowing as battered property prices and high unemployment show signs of stabilising.
"The banks have been under pressure to take more decisive steps to deal with troubled mortgages and this may be a sign that they are starting to make progress," said Philip O'Sullivan, chief economist at NCB Stockbrokers.
"The stabilisation in unemployment in particular and the return to growth of hiring in the private sector is very important and that should mean that the pace of new arrears formation continues to fall over the course of 2013."
The central bank said the number of mortgages that had been restructured fell by 2 percent as more permanent solutions were found and that the level of customers in arrears for less than 90 days fell to 49,363 from 50,031 in the previous period.
Demonstrating how deep the problem is for those who bought houses before a property crashed halved the average price of an Irish home, however, homeowners in arrears for more than 720 days rose 14 percent to account for 3 percent of total stock.
The bank released detailed figures for problem loans of investors for the first time late last year and said on Thursday that the proportion of buy-to-let mortgages in arrears rose to 18.9 percent from 17.9 percent at end-September.
Bank of Ireland, which has the lowest proportion of arrears in the sector, said this week that it was confident that mortgage arrears among its customers were stabilising after the rate of growth continued to slow.
The banks have come under heavy criticism for being slow to deal with arrears, although Ireland's financial regulator said last month that they had made big improvements in preparing to manage the problem.