"By complying with government requests, companies are unlawfully participating in mass and indiscriminate surveillance and are in breach of Article 8," said Privacy International.
In July, Privacy International brought a claim in the Investigatory Powers Tribunal (IPT), challenging Tempora and GCHQ's access to the Prism programme.
"Unless the companies provide a satisfactory response, Privacy International will be adding them as respondents to its IPT claim," it said.
For their part, when their identities were made public in relation to Tempora, a number of the telecoms companies last week said they complied with all UK and international laws when it came to data protection.
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