Rudd welcomed the Sky News commentator's on-air apology on Monday night, confirming it was part of a defamation settlement.

"I'm pleased to say that Murdoch's Peta Credlin -- the Liberal Party mouthpiece masquerading as a journalist -- has settled my complaint against her for defamation," the former Labor leader said on Twitter.

"The terms are confidential, but here's the on-air apology for her false claims."

Rudd said his lawyers had earlier sent Credlin a letter demanding an immediate apology after her claims last year.

Credlin, a former chief of staff to Tony Abbott, had accused Rudd of using his petition to harvest email addresses to "bombard people with hard-left propaganda and urge them to boycott the Murdoch media".

But Rudd said it was impossible for him to access the email signatures on the parliamentary petition site. Credlin confirmed this in her apology.

"I said the petition was a data harvesting exercise and that Mr Rudd now had more than half a million email addresses to use for his own political purposes," Credlin said.

"That was false. Mr Rudd did not have access to the email addresses in the petition because they were the property of parliament, nor did he seek them."

Rudd's petition to launch an inquiry into the power of Murdoch's media empire reached half a million signatures in November.

Australian Associated Press