The European Central Bank's (ECB) single supervisory mechanism for the banking union may need clearer powers to implement its clean-up efforts for non-performing loans (NPLs) in the eurozone, a European regulator has warned.

"The ECB is creating a common yardstick to define and measure NPLs, which is already great progress. But the enforcement process, such as administrative fines, will still be decided by national supervisors under national law," said Maria Nieto, assistant director-general