Western Australia's plan to introduce "post and boast" laws has drawn criticism from a coalition of 21 organisations, who argue the proposal is not backed by evidence and will further disadvantage the state's most vulnerable people.

The laws would make it illegal for offenders to share footage of their crimes on social media, as part of a national push by states and territories to crack down on youth crime.

In a letter to WA Premier Roger Cook, Attorney-General Tony Buti and other MPs, the coalition — led by Social Reinvestment WA (SRWA) and including several First Nations organisations — warned the laws would drive more young people into an already stretched justice system.

While supporting efforts to reduce harm and improve safety, the groups argue the bill "does not address the root causes of offending and is likely to further entrench disadvantage".

"The Bill also poses serious risks to fair process in our legal system. Significantly, it may be utilised to silence civil disobedience, free political expression, satire, and other legitimate forms of expression that are fundamental to our democracy," the letter, authored by SRWA Chief Executive Sophie Stewart, states.

Ms Stewart said relying on police discretion alone was inadequate and, without "consistent, transparent and accountable frameworks", there was a "high risk of racial and class-based enforcement disparities".

Peter Collins, Director of Legal Services at the Aboriginal Legal Service of WA, said the "breadth and scope" of the laws would have a "disproportionate impact" on First Nations people, noting even WA Police concede there is "limited evidence" the problem is widespread.

In a separate, earlier letter to Mr Buti, Mr Collins stressed the risks would fall heavily on Aboriginal children and young people, who have "long been, and continue to be, over-policed and overrepresented in Western Australia's criminal justice system".

He also warned the bill, as drafted, could see people convicted for sharing footage of an offence even if no one had been prosecuted for the offence itself.

Similar laws were passed in Victoria last week and are already in place in NSW, Queensland, South Australia and the Northern Territory. Announcing Victoria's version, Attorney-General Sonya Kilkenny said: "These laws send a clear message to offenders that there are serious consequences for posting and boasting."

Her comments echoed those of South Australian Attorney-General Kyam Maher, who in May said: "Criminals can seek to gain notoriety by posting and boasting which could potentially incite or encourage others, and further embolden their own illegal acts. This legislation is an important step forward in protecting the community from offenders who seek to glorify illicit activities."

But legal and human rights groups across the country have dismissed the approach as harmful and unnecessary, arguing it duplicates existing sentencing powers and will only increase the number of children in custody. Judges and magistrates can already treat posting crimes online as an aggravating factor.

WA's draft laws propose the harshest penalty in the country — up to three years' imprisonment. The bill will go before a parliamentary committee before being voted on. Ms Stewart called the punishment "excessive, particularly considering there is no evidence this approach will support community safety".

She also said the framing of the bill suggested it was aimed at young Indigenous people in regional and remote communities.

"This is especially troubling given the federal and state government have committed to Closing the Gap, including reducing Aboriginal incarceration rates," she said.

Mr Collins pointed to reports from NSW and Queensland showing the "overwhelming majority" of people charged under such laws are children.

"ALSWA notes that available statistics indicate the majority of charges lodged in the Children's Court of Western Australia are brought against Aboriginal young people, many of whom have complex neurodevelopmental and social vulnerabilities," he said.

Ms Stewart said WA's proposal reflects a "broader punitive shift that fails to address the underlying causes of behaviour and instead reinforces cycles of contact with the justice system."

The Australian reported that last week's meeting of the Standing Council of Attorneys-General in Sydney descended into turmoil, with states and the Northern Territory insisting they would prioritise election promises — even if that meant locking up more children — over Closing the Gap reforms.

The number of Indigenous people incarcerated has continued to rise, with laws across all jurisdictions seeing more children and young people held on remand for extended periods.

"Western Australia's justice system and prisons are already under significant pressure," Ms Stewart wrote.

"We have recently seen the most significant youth justice crisis this state has ever faced, resulting in two children dying in custody. Every adult prison is over capacity, with three people sleeping in cells designed for one in Hakea. Introducing new laws that funnel more people into a system already failing to rehabilitate will only deepen harm."

Mr Collins agreed.

"Punitive and highly politicised 'tough on crime' policies inevitably increase police interactions with Aboriginal people, broaden the circumstances in which harsher penalties may be imposed upon conviction for offending, and increase the likelihood that Aboriginal people who enter the justice system will reoffend or remain in the system for longer periods," he said.

"They are knee-jerk reactions, often to sensationalised media coverage, that do not address the drivers of the behaviours they seek to discourage."