Sander Banks are controlled by legislation from both national and international authorities.
They are however not authorities themselves and therefore have no mandate to investigate a customer whilst breaching their privacy besides the intelligence they already have.
In the agreement I have with bunq, we agreed that they will facilitate my banking, for which I will pay them. Banking being a continue service where my money is gathered, stored and delivered to me at certain moments when I request so.
The agreement did not state that bunq has unlimited access to any other information but which is required to deliver the promised service.
Nor does any law oblige me to disclose any private information to a bank, other than that information that is needed to prove my identity, which I did upon registering myself.
Law does however require bunq to facilitate me with a bank account with basic features, such being the ability to deposit and withdrawal my money via payments or transactions.
When bunq wants to suspend my account, they must have a dammed good reason for that. They are obliged to deliver me a continuous service and when they want to be released of that obligation, they have to disclose why they should want that.
When they infringe the agreement they made with me, they are liable for the costs I have made in the suspicion that I was delivered a continuous service (which means all the subscription fees) and for the costs I will have to make to transfer and get all of my services that bunq delivered to me.
In this case bunq asks for intelligence they want from the account owner. They ask him to disclose information he is not obliged to disclose and refuse to elaborate why this information is needed.
Then they tell that when the information is not disclosed, they will breach the agreement they made, without giving any further reason why.
A lawyer is going to have a field day with this matter when bunq terminates the agreement unlawfully.
So bunq first has to disclose (under GDPR) why they need this intelligence and how, when and what it is being used for.
When they wish to terminate the agreement, they too have to give a very good reason why they want this.
When they have a fundament suspicion of fraud, they should let an authority investigate it.