In a statement, Roy Morgan said Facebook/Meta, Telstra, News Corp and Amazon rounded off the top five distrusted companies.

The research firm said the change in the top rank occurred after the Optus data brach in September 2022, at which time there was an immediate and sharp increase in distrust of the brand.

While this had eased in the months following the breach, monthly levels were much higher than previous levels, it said.

Roy Morgan chief executive Michele Levine noted that brands which suffered major scandals found that once distrust took hold, it was very difficult to curtail.

She said while incremental improvement in distrust may be evident on a monthly basis, residual distrust did not just vanish.

The top 10 companies in the most distrusted list. Courtesy Roy Morgan

The company's ongoing research on trust and distrust over many years had shown that while events became less "top of mind" due to new "distrust-generating" events, it would be wrong to believe this meant a brand has become trusted again.

Affected brands remained vulnerable, and by assessing Net Trust/Distrust over a 12-month period rather than the latest month snapshot only, the cumulative effect on a brand showed through.

“Distrust makes a brand fragile and is a powerful driver in the decisions which consumers make,” Levine said. “Brands need to be aware of the ongoing dangers that distrust presents, with lingering distrust a significant risk.”

The latest ranking change for Optus spells continued bad news for the telecommunications industry. Roy Morgan reported this industry had become the most distrusted industry in the economy in February 2023 and this continues to be the case in the year to June 2023.

Roy Morgan said the data breach at medical insurer Medibank in October 2022 had affected the company which was now the sixth most distrusted brand.

TikTok had also witnessed a big increase in distrust over the past quarter, falling five places to become the eighth most distrusted brand in the economy, and replacing Twitter/X as the second most distrusted social media brand.

The research company noted that its results came before Elon Musk rebranded Twitter as X.

Apart from the top 10, Qantas' trust levels had fallen, and it is now the 13th most distrusted brand in the economy (deteriorating six distrust rankings from 19th in the year ending March 2023).

Qantas was even more distrusted than its own budget airline, Jetstar, which was the 16th most distrusted brand.