U.S. consumers defaulted on credit in December at a rate of 2.24%, the highest rate since 2.3% in April, according to an index by Standard & Poor’s and Experian.

Credit defaults increased two basis points from 2.22% in November, though they declined from 3.01% in December 2010.

S&P said mortgage defaults drove the overall increase, as first-mortgage defaults rose to 2.19% from 2.17% in November. Those mortgages saw a 1.92% default rate in August.

Second-mortgage defaults ticked up to 1.33% from 1.26%.

“The second half of 2011 saw a slight reversal of the two-year downward trend in consumer credit default rates,” said David Blitzer, managing director and chairman of S&P’s index committee. “First mortgage default rates rose for the fourth consecutive month, as did the composite.”

Auto loan defaults increased as well to 1.27% in December from 1.17% a month earlier.

Bank card defaults, however, dipped to 4.6% from 4.91% in November, and declined from 6.73% in December 2010.

Regionally, Miami’s consumer debt default rate rose to 4.73% from 4.47% in November, though that’s down considerably from 10.15% in December 2010.

Write to Andrew Scoggin.

Follow him on Twitter @ascoggin.