Serious delinquencies increased for the 32nd consecutive month as the US prime jumbo (a prime mortgage that is too large to qualify for favourable treatment by a government agency) mortgage performance continued to weaken during January 2010, according to Fitch Ratings.

Prime jumbo loan delinquencies started to rise in Q2 2007, however they accelerated in 2009 and almost tripled over the course of the year. Florida saw the biggest monthly jump of the five states with the highest volume of jumbo loans outstanding.

Vincent Barberio, managing director of Fitch, said: "The new year has brought no relief from declining jumbo loan performance. The trend line for delinquencies indicates the 10% level could be reached as early as next month."

The five states with the highest volume of prime jumbo loans outstanding comprise approximately two-thirds of the loans in question. Prime jumbo RMBS 60+ days delinquencies for these states at January 2010 compared to December 2009, and their approximate share of the $381bn market, are as follows: California, 11.3%, up from 10.8% (44% share of the market); New York, 6.1%, up from 5.8% (7% share); Florida, 16.6%, up from 16% (6% share); Virginia, 5.6%, up from 5.4% (5% share) and lastly New Jersey, 7.4%, up from 7.1% (4% share).

Prime jumbo borrowers that were up-to-date on their mortgage for the previous month but missed a payment the following month (the roll rate) fell slightly to 1.2% for January from the seasonal high of 1.3% in December 2009, but remained above the 1% monthly average for 2009.