The lender hopes to offset the drop by growing its loan business as well as by expanding its business with corporate and very wealthy clients, the report said, without giving any further detail of why customer numbers were expected to decline.

It also didn't say if any specific category of client was most likely to be lost.

Commerzbank declined to comment.

According to the bank's website it serves around 11.6 million private and small-business customers in Germany and more than 70,000 corporate and other institutional clients worldwide, so the reported loss of customers would suggest a drop of around 15%.

The bank earlier this month reported a $3.3 billion fourth-quarter loss, sinking further into the red as it continued a major restructuring and dealt with the fallout of the COVID-19 pandemic.

The bank's restructuring plan involves cutting 10,000 jobs and closing hundreds of branches in the hope it can remain independent.

($1 = 0.8253 euros)

(Reporting by Christoph Steitz and Tom Sims; Editing by David Holmes)