Australia’s telco sector is bracing for a regulatory decision that could significantly shrink Telstra’s claimed mobile coverage, as rivals TPG Telecom and Optus intensify pressure on how network reach is measured.

The Australian Communications and Media Authority (ACMA) is expected to rule on whether mobile coverage maps should adopt a stricter signal threshold of -115 dBm – a level at which users can reliably make calls, send texts and access data.

Telstra currently uses a broader -122 dBm benchmark, which captures weaker, less consistent coverage.

If adopted, the change could wipe up to a third of Telstra’s touted 3 million square kilometres of coverage from official maps, narrowing the perceived gap with competitors. Optus claims 1.1 million square kilometres of coverage, while Vodafone owner TPG reports around 1 million.

TPG has been particularly aggressive, submitting test results to regulators that challenge Telstra’s “full coverage” claims in regional areas. The company alleges some locations require external antennas to function, contradicting Telstra’s marketing.

Telstra chief executive Vicki Brady has rejected the claims, describing them as “serious allegations” and defending the company’s methodology.

Telstra argues that coverage cannot be defined by a single threshold and points to internal testing, including a 60,000km nationwide drive program, showing usable service even at weaker signal levels.

The telco also warns that restricting how coverage is represented could dampen investment in regional infrastructure.

The outcome is unlikely to change Telstra’s network advantage but is expected to weaken its marketing edge and pricing power, particularly among customers willing to pay a premium for perceived superior coverage.