The Office of Competition and Consumer Protection (UOKiK) said its head, Tomasz Chróstny, "opposes banks' plans to introduce negative interest rates on deposits of individual customers."
The watchdog added that such moves "could undermine the already strained public confidence in the banking system" and "lead to large-scale withdrawals of savings."
In a letter to 23 banks, Chróstny "has expressed his concerns and demanded clarifications" about any steps "being taken in this matter," according to the uokik.gov.pl website.
Referring to media reports and announcements by the Polish Bank Association (ZBP), the watchdog said that the potential introduction of negative interest rates on deposits would force consumers "to pay the banks for their savings."
"The introduction of negative interest rates on deposits would affect consumers and cause a number of macroeconomic risks," Chróstny was quoted as saying.
He argued that such steps would "force consumers to look for alternative and not always safe ways of investing their money."
"Additionally, if consumers started to withdraw money from banks and decided to keep it at home, the scale of theft and fraud against consumers would most likely increase," Chróstny warned.