Dutch central bank president Klaas Knot has ‘fundamental questions’ about ING’s plans to sell information about customers’ spending habits to advertisers, he told RTL news on Thursday.

‘Is this the innovative way of earning money we should be striving for?’ Knot said. ‘I don’t think this is what we should be doing, but I will give ING one chance to convince me my concerns are misplaced.’

Earlier this week the Financieele Dagblad reported that ING plans to start trials involving around 1,000 customers who will agree to targeted advertising based on their spending patterns.

‘I am extremely critical of this idea,’ Knot said. ‘You can see in the reactions that people are extremely worried this will get out of control.’