The Dutch competition authority NMa has been investigating the countries' three biggest banks, ABN Amro, ING and Rabobank, over alleged cartel activities, the Dutch newspaper Financiele Dagblad reported Wednesday.
The NMa had raided the three banks in the past two days to investigate suspected price-fixing of the interest charged on business loans, the banks confirmed Tuesday.
Teams from the NMa copied documents and confiscated computers temporarily from the banks. A number of staff members were also questioned.
Spokesmen for the banks said the operation was entirely unexpected and the scope of it was unprecedented. But they said they were unaware of any irregularities.
The competition authority had warned on a number of occasions recently that the financial sector was to become its top priority in the near future. But the banks said the NMa had kept them in the dark about the exact nature of the suspicions.
The competition authority would not comment on the matter, but a spokesperson for ABN Amro believes the NMa suspects that the banks made cartel agreements about the interest and surcharges on businesses loans.
The three banks together control the Dutch market for business credit.
The banks say that they follow the official European interest rates when setting their basic fees for corporate credit. If the European Central Bank raises the interest rate, the banks usually follow suit within about a week.
However, the basic interest rate for companies can, depending on the risk profile, be increased with a surcharge.
It is understood that the NMa suspects the three banks of agreeing a specific surcharge in advance. This could be to the disadvantage of small and medium-sized businesses.
The banks say they are giving full cooperation and they expect further visits from the competition authority, as the investigation is ongoing.