The move follows claims that Singapore had spied on Australia for 20 years.
A report by Reuters said Defence Minister Peter Reith is standing by the government's decision to green light SingTel's bid, despite the fact that Australia's military satellite communications are managed by C&W Optus.
Reith said the government had received assurances from the Singaporean carrier that C&W Optus' involvement in military communications would be safeguarded.
"I have available to me a range of advice which is expert in all of these matters and I am quite satisfied with the advice that I've had and we are satisfied with the arrangements that we have been able to put in place," Reith told Reuters.
The Australian Democrats have also joined the fray, urging the Government to further investigate the takeover bid.
The spying claims follow reports that the Singaporean government had used SingTel to spy on its own people, raising concerns about the possibility of intercepted emails and phone calls.
-All I would say is that people, I would hope, would be reassured that the Australian government is in the best position to make decisions of this sort and we've made some decisions," Reith said.
SingTel's bid for C&W Optus has yet to officially receive final Australian government approval.
