Optus has written to the competition regulator claiming that rival Telstra has blocked a 5G push for 2.5 million regional Australians and demanding a probe into the allegedly anti-competitive conduct, which could delay any return on the $1.5 billion that the Singtel-owned telco spent on spectrum late last year.

Spectrum determines how much capacity a given mobile network can carry over certain distances or bands – the more, the better for network operators Telstra, Optus and TPG that license slots from the government for set terms.