Telstra agreed more than a decade ago to store huge volumes of electronic communications it carried between Asia and America for potential surveillance by United States intelligence agencies.

Under the previously secret agreement, the telco was required to route all communications involving a US point of contact through a secure storage facility on US soil that was staffed exclusively by US citizens carrying a top-level security clearance.

The data Telstra stored for the US government includes the actual content of emails, online messages and phone calls.

The US Department of Justice and Federal Bureau of Investigation also demanded that Telstra "provide technical or other assistance to facilitate ... electronic surveillance".

In 2001, when the "network security agreement" was signed, Telstra was 50.1 per cent owned by the Commonwealth Government.