Bring up the past ... Bill Shorten walks behind Julia Gillard in Question Time in Canberra. Source: News Corp Australia

Mr Shorten told 3AW radio at the time he hadn’t met with Mr Rudd on the night of the 2013 parliamentary midwinter ball, but it was revealed on the ABC’s The Killing Season program that he had and he now regrets the remarks.

Liberal senator Arthur Sinodinos told Sky News the lie could be Mr Shorten’s “carbon tax moment” — a reference to former prime minister Julia Gillard’s broken election promise.

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He lied ... Bill Shorten and for prime minister Julia Gillard. Source: News Corp Australia

Neil Mitchell who interviewed Shorten said his confession was not enough to clear his name.

“The Opposition Leader has failed to publicly concede he lied, only saying he “regretted” his words,” Mitchell said.

“He can’t say it and he can’t accept it, but it was a lie.

“It was a political lie for reasons that are obvious. It was a lie to me and, more importantly, it was a lie to you.

“Admit it, apologise and move on.”

Deputy Labor leader Tanya Plibersek however is standing by Bill Shorten after the opposition leader admitted he lied about the meeting.

While Julia Gillard says she thought Kevin Rudd was 'relieved' after his leadership spill, Rudd says it's what an assassin would say. Courtesy: The Killing Season/ABC

“That’s enough ... you should be holding the prime minister to account,” she told reporters in Canberra on Thursday as they quizzed her about the admission and whether Australians could still trust the Labor leader.

“Why don’t you ask Tony Abbott if he ever lied about saying no cuts to health, no cuts to education, no changes to pensions, no cuts to the ABC.”

Ms Plibersek earlier told the ABC that Mr Shorten was talking about “ancient history” when he regretted the answer he gave on talkback radio in June 2013, days before he switched sides to restore Mr Rudd to the leadership.