Spark chief operating officer Mark Beder said it was a significant, essential upgrade to our oldest network and would provide a future-proof platform for the latest voice technology.
It would also allow Spark to deploy new services.
"We've been talking about doing this for over a decade now and many other countries are also in the process of retiring their PSTNs, so it's great to finally be able to get on with it here," Beder said.
Maintaining the current network was becoming harder as it aged, with some components no longer manufactured.
"We've bought every second-hand part we can source from around the world and people with the skills to maintain the technology are harder to find."
Beder added that although the project was a massive technical and logistical undertaking, it would be largely invisible to customers.
"The vast majority of customers won't need to do anything and their existing phones and devices will continue to work normally when they switch from the PSTN to the new IP-based network."
However, some customer devices such as low-speed dial up services such as some medical and house alarms, old SKY decoders, old Eftpos terminals may be affected.
Beder said Spark would work with vendors and customers to make the transition as easy as possible, but some customers may need to talk to their alarm companies and third-party providers.
The new network also has implications for emergency services as it may affect the way emergency calls are made.
Spark had already met with emergency services and Beder said they'd had a positive reaction to the planned changes.
