West Coast residents have been asked to protect the broadband fibre optic cable after the eastern cable was lost in the earthquakes early yesterday.
In a statement, Spark said broadband services are reliant on the integrity of the western cable, which runs from Blenheim and Nelson down to Christchurch, via Greymouth.
If this cable was also damaged, "it would seriously degrade connectivity for much of the South Island".
To increase protection of this cable, Spark has cancelled permits for any earthworks or maintenance along the length of the cable.
"We would ask for the assistance of New Zealanders who live along the length of the cable to ensure that they protect against any risk of damage," a Spark spokesman said.