The move has been made using emergency Covid-19 powers and favours company directors, they say.

A surprise move by treasurer Josh Frydenberg to make shareholder class actions harder has been slammed by lawyers as cronyism that gives company directors the green light to hide bad information from investors.

“If bad directors take advantage of this change to lie to shareholders and people whose savings are in superannuation, the treasurer will share responsibility,” Jacob Varghese, the chief executive of law firm Maurice Blackburn, told Guardian Australia.

Ben Phi, the managing director of class action firm Phi Finney McDonald, said the move was “completely to be expected from a government with a strong and improving track record of cronyism”.

“The Morrison government has used a public health crisis to secure emergency powers, which they are now using to serve the interests of their big business mates,” he said.

In a statement released late on Monday afternoon, Frydenberg significantly raised the bar that lawyers will have to meet to hold directors liable for misleading their investors.

Frydenberg made the change using regulations under emergency powers granted by parliament to deal with the coronavirus emergency that will last for six months.

They change the existing requirement that a director needs to act reasonably to avoid liability for misleading the market to a new test where they will have to have acted with “knowledge, recklessness or negligence” to be in breach.

Varghese said the change was not necessary because existing rules already had exemptions for when information was uncertain.

“The risk is that this change allows companies to hide bad news that has nothing to do with Covid-19,” he said.

“There should be no green light for company directors to hide information from the people who actually own a company.”

Phi said responsible companies had responded to the coronavirus crisis by withdrawing their profit guidance – a move that in some cases prompted their share prices to plunge.

“None of those price falls have resulted in class actions,” he said.

“They are the consequence of a company complying with its disclosure obligations rather than breaching them.”

Frydenberg’s move, announced in a seven-paragraph press release issued at about 4.45pm on Monday, caught class action lawyers by surprise.

It followed the treasurer’s decision on Friday to force litigation funders to hold financial services licenses – something opposed by the corporate regulator.

The attorney general, Christian Porter, has also announced a parliamentary inquiry into class actions and litigation funders.

Company directors and industry groups have been campaigning fiercely against class actions since late last year.

The business peak body, Ai Group, has raised concerns about both shareholder class actions and ones mounted by workers under the Fair Work Act, with chief executive Innes Willox claiming in October that claims in the previous financial year totalled more than $10bn.

In December, the Australian Institute of Company Directors complained that it was too hard for directors to defend their decisions in class action cases because no proof of “intention, recklessness or negligence” was required.

“The heightened level of uncertainty around companies’ future prospects as a result of the crisis also exposes companies to the threat of opportunistic class actions for allegedly falling foul of their continuous disclosure obligations if their forecasts are found to be inaccurate,” Frydenberg said on Monday.

“In response, companies may hold back from making forecasts of future earnings or other forward-looking estimates, limiting the amount of information available to investors during this period.

“The changes announced today will make it harder to bring such actions against companies and officers’ during the coronavirus crisis and while allowing the market to continue to stay informed and function effectively.”

Guardian Australia is not aware of any coronavirus-related shareholder class actions that have been lodged in Australia since the crisis began.

However, Qantas staff have mulled a class action against the airline for allegedly failing to protect them against Covid-19.