Some recipients are required to supply paperwork from up to five years ago, but Mr Porter said that applied to a "very small number" of people.
He added that the system had recovered $300 million since the start of the financial year.
"What this system is doing is raising real debts around real overpayments based on real cross referencing of evidence," he said.
But Shadow Minister for Human Services Linda Burney said it should be suspended, citing "inherent problems right across the system".
Ms Burney told the ABC on Monday that she had written to the Minister over the matter, citing an "enormous number of complaints".
"It's an automated system that has clearly got enormous problems," she said.
"Why should it be the recipients' responsibility to prove they're right when the Government is making the mistake?"
Ms Burney today tweeted that the system needed to "get it right before threatening people", referencing the #notmydebt social media campaign launched in response to Centrelink.