Centrelink has been accused of intimidating clients with text messages warning them against committing welfare fraud, only days after it was attacked for using the AFP's logo on letters to customers.
The agency has sent the messages to welfare recipients telling them its fraud crackdown, Taskforce Integrity, was operating in their area and urging them to update their personal details.
Critics have blasted Centrelink for the text messages, saying they were 'intimidating' and 'threatening' to welfare recipients, and accusing the government of being callous towards people with mental illness.
But the Department of Human Services says the messages are meant to educate people about their obligations.
The agency came under fire last week after it sent letters emblazoned with the AFP's logo, telling clients to keep their personal details up to date, before listing a series of penalties if they commit welfare fraud, including a prison sentence and a criminal record.
The DHS started Taskforce Integrity to detect welfare fraud with the AFP in 2015 and has targeted areas it says have a higher risk of non-compliance. In July, it sent 38,000 letters to clients in Burnie, Tasmania, Mirrabooka, Western Australia, Liverpool, NSW, and Dandenong, Victoria.
It is understood the department since 2015 has sent more than 85,000 letters with the AFP logo to welfare recipients in nine locations around the country.
Greens senator Rachel Siewert said the government was deliberately trying to intimidate vulnerable people who had done nothing wrong.
"I'm aware of one young recipient of these messages who is on [Disability Support Pension] with psychosocial disability. How can the government claim to take mental health issues seriously and then treat those with mental ill-health so callously?" she said.
"This is the action of an authoritarian government and shows contempt for people, fairness and process."
The DHS said it only text messaged people who previously indicated that they could receive messages via SMS, and who had recently received a Taskforce Integrity letter.
Centrelink has sent 25,000 text messages to clients in Mirrabooka, Liverpool, Dandenong, and Burnie.
Australian Council of Social Service chief executive Cassandra Goldie said the government's campaign involved "an untenable level of harassment and intimidation of people on low incomes."
"Put yourself in the shoes of someone who gets this kind of message when they are struggling to make ends meet and get through to Centrelink," she said.
"The government has a high duty of care to people who are accessing income support payments because they are often vulnerable, but these texts come across as warnings.
"[The] government must cease this inappropriate action against people receiving income support payments."
Centrelink sent the text messages and letters after prolonged criticism of the wording of notices it sent to welfare recipients about possible 'robo-debts', and after DHS officials were forced to defend them in a Senate inquiry.
Centrelink has been embroiled in controversy over its online debt-raising system which automatically compares information clients supply to the welfare agency with data given to the Tax Office and raises debts based on any perceived discrepancies.
A parliamentary committee found the DHS' 'robo-debt' effort should stop immediately because the program had a "profoundly negative impact on the lives of thousands of Australians."
Senator Siewert said the government had learnt nothing from the Senate inquiry findings that found flaws in its communications with income support recipients.