When the COVID-19 pandemic first began, public health officials said it was not an airborne disease and instead travelled by droplets from the nose or mouth.

Experts who suggested that may not be the case were sometimes shouted down, and the opinion was sometimes lumped in with misinformation and outright conspiracy theories online.

As evidence mounted COVID could indeed spread through the air, officials were forced to reverse their opinion.

In the aftermath of the pandemic the federal government has moved to curb the easy spread of misinformation and outright lies on social media.

But legal experts worry the proposed laws could end up undermining the truth.

Constitutional law expert Anne Twomey says if the Albanese government's proposed misinformation and disinformation laws were in place in 2020, the correct information about COVID-19 could have been wiped from social media.

"By excluding those possibilities you actually give yourself the harm that you said you were trying to avoid," Professor Twomey told a parliamentary inquiry into the matter.

The same inquiry has heard concerns the bill could infringe on freedom of speech, and that its method for assessing what is true online and what is not is flawed.

With just a fortnight to go in the parliamentary calendar for this year, time is ticking down for the federal government to pass its proposed laws.

Here is a refresher of what the bill does, and what might happen next.

What does the bill do?

The aim of the bill is to force tech companies to crack down on misinformation spreading online.

The laws would fall under the authority of the Australian Communications and Media Authority.

ACMA would not be tasked with taking down individual posts but would instead look to get the social media platforms to self-regulate, with the option of introducing a code of standards if that fails.

The bill would also give ACMA extra powers to gather information to ensure platforms meet their obligations, and if they don't, they'd face penalties ranging up to a fine of 5 per cent of their global revenue.

Minister for Communications Michelle Rowland said for something to be deemed misinformation and disinformation under the laws, it would have to both be "seriously harmful and verifiably false".

She cited examples of the disinformation spread following April's Bondi stabbing or content urging people to not get government-approved vaccines.

The laws would not deem content as misinformation if it's used for satire or within news, or if it's academic, artistic, scientific or religious.

Fact checkers 'often get it wrong'

But there are concerns even within those narrow bounds that there is the potential for unintended consequences.

One of the key questions experts have raised is if the bill requires misinformation to be content that is "verifiably false", then who would be the decider of what is false and what is true?

Barrister James McComish from the Victoria Bar Association told the inquiry he was concerned about making a government agency an arbiter of truth.

"It's not merely whether ACMA is rightly or otherwise described as a 'ministry of truth' by determining what is or isn't true, there's also the problem ACMA or, possibly worse, platform operators decide what the official party line is — whether or not it's true," Mr McComish said.

Professor Twomey also told the committee about the dangers of allowing social media platforms to define truth.

"The squillions of posts that are made, and then making those really fine assessments about what is serious harm in Australia, to our economy; [there is] not a hope that anyone in America knows any of that stuff," she said.

"If you look at the bill they just seem to rely on fact checkers."

She said from her own experience being asked for her expert opinion by fact checkers, that process is flawed.

"The problem with expertise is the expert might have it, but the person writing the fact check doesn't and they often misunderstand the experts, so they often get it wrong," she said.

"The impression I get is that these are most frequently young kids out of university and they're taking on this really important role that will lead to Meta or Google or whatever to make decisions about what is true and what is false, when the fact checker themselves hasn't properly understood what the expert has said."

She also said it was a process that could easily be impacted by asking several experts on one side of an issue to achieve a consensus.

Concerns of 'grave danger to freedom of expression'

Mr McComish said the Victorian Bar also has fears that the laws will be a "grave danger to freedom of expression".

He said the explanatory memorandum, a document which explains how the bill would take effect, contained details that concerned him.

"The inclusion of opinion and claims within the definition of misinformation ... is what gives us grave concern," he said.

"Our concern about the overreach of the bill has taken on a new life in a very disturbing way."

Professor Twomey said her reading of the bill was that content could be deemed misinformation if it was reasonably verifiable as false and misleading, but the supporting document brought that into question.

"If you look at what is says in the explanatory memorandum, it says we're not just dealing with facts here," she said.

"We're dealing with opinions, commentary, claims and invective and you can't prove those things are false, you can't prove that someone's opinion is false, it's an opinion."

The Coalition remains firmly opposed to the proposed laws.

That will require the government to win the support of the Greens and at least three crossbenchers to pass the legislation.

With crossbencher Tammy Tyrrell announcing this afternoon she also would oppose it, the pathway for the government is growing narrower.