The firm running the robodebt class action has received thousands of calls, after opt-out notices were sent to potentially hundreds of thousands of current and former Centrelink recipients this week.
Gordon Legal said on Friday it was experiencing an "unprecedented number of calls from thousands of people who received notices in their myGov accounts today".
"If you are having difficulty getting through, info about the robodebt class action is on our website," the firm tweeted.
The Federal Court had ordered the federal government to contact every person who my have been affected by the debt-raising program by May 25.
The Commonwealth could be forced to pay back hundreds of millions of dollars collected through the "online compliance intervention", which was paused last year after advice that the program was in fact unlawful.
More than 13,000 people have registered their interest in the class action so far.
It comes as the federal government continues with its crackdown on class actions.
Treasurer Josh Frydenberg announced on Friday third-party litigation funders would be subject to greater regulatory oversight.
The firms - which cover the cost of the class action in return for a percentage of damages awarded - will be required to hold an Australian Financial Services Licence and comply with the managed investment scheme rules.
Attorney-General Christian Porter also instigated parliamentary inquiry into the class action industry last week.
Labor's attorney-general spokesman Mark Dreyfus and financial services spokesman Stephen Jones said the Treasurer's announcement proved the inquiry was a "sham" and had "cherry-picked" an idea that had been rejected by the Australian Law Reform Commission as unlikely to work.
"It's no coincidence that inquiry was first proposed in March just days after 10,000 victims of the Morrison Government's cruel Robodebt scheme signed-up to a class action to defend their legal rights," they said in a statement.
A spokeswoman for Gordon Legal confirmed the robodebt class action was not backed by a third-party litigation funder.