The Information Commissioner’s Office (ICO) in the UK is probing an incident in which payment service provider Klarna sent an email to customers who had not opted in to receive it.

As of this morning, the ICO had received more than 90 complaints from members of the public.

An ICO spokesperson said: ”Businesses should only contact individuals for electronic marketing purposes where consent has been provided or, in limited circumstances, where they have an existing relationship with a customer. Some members of the public have made us aware of an email sent by Klarna and we will be making enquiries.”

Klarna, a Swedish provider of payment solutions,  mistakenly sent a marketing email to people who had not opted in to receive the weekly newsletter.

“Human error” meant that the email was sent incorrectly, and the company has apologised for the mistake, which prompted complaints from some who didn’t realise they had used the company’s services.

The company’s checkout technology, which processes credit and debit card transactions, is used by some retailers to process online payments.

Klarna said: “The email was sent to Klarna consumers who have recently used one of Klarna’s products or services including Klarna’s checkout technology. When you use Klarna you agree to our terms and conditions and our privacy notice.”

It added: “Please rest assured, you have not been added to a marketing database. In accordance with our internal policies you will not receive any further newsletters unless you opt in or download our app at a later date.

“We are currently investigating how this happened, and are taking action to ensure nothing like this can happen again in the future.”