In a Transparency Report released Friday, Vodafone revealed that the governments of six countries have the ability to tap directly into its communication network to spy on customer calls, with no need for a legal warrant. The British telecommunications company did not reveal which governments exercised this power.

“In a small number of countries the law dictates that specific agencies and authorities must have direct access to an operator’s network,” the report said. “In those countries, Vodafone will not receive any form of demand for lawful interception access as the relevant agencies and authorities already have permanent access to customer communications via their own direct link.”

Vodafone, the world’s second-largest carrier behind China Mobile, released the report to detail how governments requested data about the company’s users for law enforcement and national security purposes. While other telecommunications companies have released domestic transparency data, this release marks the first time a multinational firm has gone public with a global data set. The report includes data from 29 countries where Vodafone operates.

While privacy advocates welcomed the disclosure, they expressed concern about the lack of legal process in the six countries that have direct access to customer calls.

“This is mass surveillance at its most severe, where government places demands against telcos for broad access to the data flowing through their wires, operating in secrecy, under unclear legal bases, without any accountability,” said British privacy watchdog, Privacy International, in a statement.

Privacy International called for the further disclosure of the six unnamed governments.

“Companies must be held to account and their secret agreements with governments regarding the monitoring of communications data must be made public.”