The three main operators in the Netherlands – KPN, Vodafone and T-Mobile – have confirmed they are under investigation by the country’s antitrust authorities over alleged cartel practices concerning the pricing of mobile services.

According to a Financial Times report, the offices of all three operators were visited by the Netherlands Competition Authority (NMA) yesterday morning following a reported tip-off by whistleblowers.

A spokesman for KPN said the NMA had been specifically investigating “concerted practice with regard to mobile telecommunications offerings on the Dutch consumer market”, as well as “the division of independent sales channels.” KPN said that five of its employees are being questioned as part of the investigation.

The two other operators also released short statements to say they were co-operating with the authorities. A spokesperson for Deutsche Telekom’s T-Mobile Netherlands added that the firm was “confident about the positive outcome of the investigation.” The NMA has yet to comment further on the nature of its probe.

The three operators have already been charged once with operating a cartel, notes the report. In 2001, they were found guilty of exchanging information about retailer handset subsidies. KPN – the market leader – was fined EUR7.9 million, T-Mobile EUR4.6 million and Vodafone EUR3.7 million.

The source of the latest probe remains a mystery. Dutch media yesterday reported that the so-called whistleblowers included a former director and a board member at one of the mobile operators, although it is not clear which one.

One source at the Financial Times said that the purpose of the visits appeared to have been to look at the pricing of mobile Internet packages for prepaid customers.

The pricing of mobile data has been a huge issue in the Dutch market this year with operators struggling to keep pace with the rise of third-party services. The Netherlands also recently became the first market in the EU to pass net neutrality legislation which prevents operators from charging for specific OTT services.