Spain's central bank handled 14,647 queries and complaints about the country's lenders, the Bank of Spain reported on Tuesday.
That's 20 percent up on a year earlier, and a new record, the institution told Spanish daily El País.
Even more damning for the banks is the fact that of the 2,833 Bank of Spain investigations where bank customers were found to be in the right, those banks only acted in 518 cases.
That means the country's banks ignored more than four in five (18 percent) of rulings against them.
In 82 percent of such cases, the banks relied on their legal and economic muscle to take no action, despite the Bank of Spain finding against them.
The central bank called this "clearly unsatisfactory".
The institution pleaded for lenders "to make an effort to take into account" central bank findings "although these are not binding under current rules".
The Bank of Spain also said it would hone in serious and systematic offences by Spain's banks.
Spain's central bank ran 7,122 investigations into the country's lenders last year.
The client was found to be right in 2,833 cases (40 percent) while banks were given the all-clear in 2,372 cases (33 percent).
Other cases were dropped because of incomplete documentation or passed on to other relevant authorities, the central bank said.