The move is expected to displace 103 technical support jobs in total, sources close to the company told ZDNet Australia.
In addition, up to 65 employees at TPG's customer service section are slated to be replaced in the near future, sources said.
In the past, the ISP -- which has at least 50,000 ADSL customers and a host of dial-up and Web hosting clients -- would normally employ between 20 and 30 technical support staff at its Sydney office on a casual basis, but now, these workers "would be lucky to get one shift per week", one source said.
While outsourcing to low-cost geographical areas has long been recognised as a potential cost-saver for Western businesses, TPG employees have been kept in the dark over the decision.
"The fact that they have not announced this to their employees displays enormous disrespect to us.
"I would not at all be surprised if one day I show up to work to find the doors locked, and a security guard outside advising me to go home as I have lost my job," another source said.
"While a lot of us don't mind that we'll soon be leaving TPG," one employee said, "it's more the fact that management is attempting to hide this from us and isn't giving any notice to find a new job."
Employees first started noticing changes when a new phone system was introduced on July 19.
On one occasion, a Sydney-based help desk worker became suspicious and began investigating an unusual -- and unidentified -- individual logging calls in the company's call queue. "The employee's shift was cut after discovering the it was someone from the Philippines ... some have even been terminated for so much as inquiring about the proposed move," one source said.
Sources said workers involved in providing technical support for dial-up customers have been the first to go, and the number of ADSL-related enquiries to TPG's Sydney centre have been dropping. This suggests that Manila is picking up the load, they said.
Workers have also found other unexplainable activities. "I've seen seen logs of Jill [TPG call centre manager Jill Chesher] activating accounts, and general account assistance for staff who are not employed in our North Ryde office, nor listed in our intranet --- which has all employees in Australia and New Zealand," one source within the company told ZDNet Australia.
TPG's partner in the Philippines has also been on a recruitment drive.
Manila-based Orchid Cybertech Services has placed job advertisements online seeking call centre expertise. Initially, all queries were directed to TPG Internet head Vitek Piestrzynski, but his details have since been removed.
ZDNet Australia contacted TPG on numerous occasions via telephone and e-mail but the company has declined to comment.