Spain's surging bad loans are spurring doubt on whether the government can persuade investors that it can clean up the country's banks without further damaging public finances.

Non-performing loans as a proportion of total lending jumped to 8.16 percent in February, the highest level since 1994, from less than 1 percent in 2007, according to Bank of Spain data published today. The ratio rose from 7.91 percent in January as 3.8 billion euros of loans soured in February, a 110 percent increase from the same month a year ago. That takes the total credit in the economy that the regulator lists as “doubtful” to 143.8 billion euros.

Defaults are rising and credit is shrinking at a record pace as 24 percent unemployment corrodes the quality of loans built up in the country's credit boom and saps the appetite of banks to make new ones. Doubts about the extent of Spain's non-performing loans problem is hurting bank stocks and driving up the government's borrowing costs on investor concern that the expense of propping up ailing lenders may add to the debt burden.