Australia's biggest telecommunications company Telstra has announced it will slash 326 jobs nationwide, with a little under one in four being sent to its operations in the Philippines.

The job losses will impact roles across sales, service, and national office teams.

"We take our responsibility to support employees through this period very seriously and we absolutely understand the impact announcements like this can have on our staff," a Telstra spokesperson said in a statement provided to the ABC.

"We constantly review the way we work to simplify our business and remove duplication to improve customer experience.

"Some of these proposed changes increase slightly the amount of work done by our partners overseas."

Perth and Melbourne will bear the brunt of the cuts, losing around one hundred jobs in each city.

The Community and Public Sector Union (CPSU) condemned the cuts, saying Telstra had sent a total of 10,000 jobs overseas including staff working in technical roles, customer service and administration.

"Telstra's future lies in investing in Australian innovation, skills and jobs," director of CPSU's science and communications division Teresa Davison said.

She also questioned Telstra's reliability in the wake of multiple mass network outages so far this year.

"Telstra is not only reducing its own capacity but removing thousands of job opportunities for future generations," she said.