Telstra has sacked hundreds of customer service and management staff from its call centres around the country and will offshore more work to the Philippines.

The telecommunications giant has not publicly announced the redundancies this week, but the Community and Public Sector Union revealed the job losses on Friday after receiving alerts from affected members. The union said 450 workers had received notices that they would lose their jobs in recent days.

A Telstra spokesman confirmed the cuts on Friday afternoon, but said 326 staff would be affected.

The Telstra job losses are nationwide, with at least 140 jobs slashed in Melbourne and the closure of an entire call centre in Perth, according to the union. Calls going to Perth centre would now be handled through call centres in Bathurst, NSW and Cebu, in the Philippines.