A Dutch internet service provider has accidentally spammed a former customer with hundreds of confidential emails.

The problem started when Albert Curvers tried to cancel his subscription with cable operator Casema. Instead of ending his service, the company sent him emails containing the confidential banking details of hundreds of its customers.

The Rotterdams Dagblad newspaper reported that Curvers got his revenge by contacting some of the people whose details he had received and telling them about the breach in security.

"The customers were horrified at the news," he said.

Casema spokesman Henk de Goede has apologised to Curvers and the other customers, but said that he was unsure of how the mistake happened.

"We want to send Mr Curvers a big bunch of flowers to say sorry," he added.