Over a million older 4G mobile phones are in danger of being blocked from making triple-0 calls due to the impending shutdown of 3G networks.

The ABC has exclusively uncovered that over a million mobile phones could soon lose the ability to call triple-0, raising concerns about Australia’s preparedness for the impending shutdown of the 3G network.

Telstra is slated to shut down its 3G network by June 30, followed by Optus in September, rendering devices reliant solely on 3G obsolete.

Despite the looming deadline, approximately 113,000 Telstra customers have yet to upgrade their 3G handsets, while Optus has not disclosed its figures. Of greater concern to the government is a subset of older 4G-enabled handsets that may lose the ability to call triple-0 once the 3G networks are decommissioned, due to their configuration.

There is apprehension that owners may not realize this until they find themselves in an emergency situation.

Communications Minister Michelle Rowland revealed she was informed in March that around 740,000 Australians were affected. However, just one month later, this figure has been significantly revised upward to more than a million.