Internet service provider XS4all said on Thursday it had cooperated with 150 requests for help in police, security service and other official formal investigations last year.
The requests included providing details of telephone and email traffic and facilitating telephone and internet taps, the company, now part of KPN, said.
But the company refused to say how many of these requests came from the security services because that information falls under the official secrets act.
XS4all, which has 5% of the Dutch market, called on other providers to go public on their involvement with criminal and security investigations. According to Nos television, UPC is considering providing the information but KPN considers the matter up to the justice ministry.