Even more galling for Mr Turnbull is that the shadow broadband spokesman has spent the best part of three years ridiculing Labor's former minister Stephen Conroy for his failed attempts to censor the internet. Matching ties: Malcolm Turnbull and Anthony Albanese at the Triple J studio. Credit:Triple J Under the last-minute Coalition plan – which was not accompanied by any press release or announcement – Australian mobile phone and internet service providers would be required to censor ''adult content'' on the internet unless users opted out. Until 8pm the Coalition's policy paper called for ''mobile phone operators installing adult content filters on phones which will be switched on as the default unless the customers proves he or she is at least 18 years of age''. This wording was changed to asking vendors to ''make available software which parents can choose to install on their own devices to protect their children from inappropriate material''.

By Thursday night, after Mr Turnbull and shadow treasurer Joe Hockey had endured excruciating radio and television interviews [Mr Hockey admitted the policy was ''news'' to him], the Coalition admitted the document was ''in error''. ''The circuit breaker was Joe's interview [on Network Ten's The Project] where he admitted he had never heard about the policy,'' a Liberal insider said. ''That's when they decided to pull the plug.'' Shortly after 8pm, Mr Turnbull tweeted: ''Policy released today wrongly indicated we supported an opt-out system of internet filtering. That is not our policy and never has been.'' Mr Turnbull, who learnt about the internet filter about 4.30pm on Thursday, had to defend the policy's merits in a live debate on Triple J's Hack program soon after.

VIDEO: Turnbull and Albanese let insults fly on-air during Triple J's Hack program Shortly before appearing on the radio show, Mr Turnbull was on the phone to Liberal MP Paul Fletcher, who came up with the idea for the filter. Mr Turnbull was trying to understand, first, how the internet filter would actually work, and second, how it differed from the filter proposed by Senator Conroy, which he had so gleefully derided. While Mr Fletcher declined to explain the background to the bungle, Fairfax Media understands that the MP, a former telecommunications executive, conceived of the filter as part of a broader plan to make the internet safer for children.

''Abbott assigns jobs, pseudo policies if you will, to promising junior MPs who he can't make ministers,'' a Liberal source said. ''[Abbott] asked Paul Fletcher to do a discussion paper on child safety online . . . but nobody knew about the filter.'' By the time he got on air, Mr Turnbull faced the excruciating scenario of having to defend a policy in his own portfolio he did not know existed several hours earlier. "What [our policy] does is essentially install that software either in the smartphone or in the modem as a default which you can switch off but then that's at your call," he said. The ABC interviewer asked Mr Turnbull how he could justify the Coalition's default internet filter ''when the public has already rejected that policy''.

''Well it's not an internet filter in the sense of what Stephen Conroy was proposing,'' Mr Turnbull ventured. ''This is a system where – and this is what the British are going to employ ... the filter will be contained in software installed in either people's smartphones or modems,'' he continued. While Mr Turnbull was on the radio, Mr Fletcher was talking to journalists. He told Fairfax Media the key to the policy was installing anti-pornography filters on every new mobile and modem sold through major telcos in Australia. ''What we are trying to do is use the power of the default so that when people get a new product, as a default [and] without them having to worry about it, this safety feature is built in,'' Mr Fletcher said, about 6pm. As soon as Mr Turnbull got off the air he began phoning staff at Liberal campaign headquarters to find out what was going on.

"All I can say to you is mistakes happen," Mr Turnbull later said. "As soon as I became aware of the policy having been released in the form it was I took steps to correct it." It is still unclear how the internet filter policy was allowed to be published in the Coalition's final policy documents two days before an election – and without going to shadow cabinet. The idea was devised by the Coalition's Online Safety Working Group, which includes Mr Fletcher, Senator Gary Humphries, Alex Hawke, Natasha Griggs, Wyatt Roy, Patrick Secker, Senator Stephen Parry, Senator Bridget McKenzie and Luke Simpkins. Last year the working group put out a policy proposal calling for products sold through vendors to meet "national standards for online safety for children". Mr Fletcher said installing porn-filtering software by default was a new development that was added to the policy in recent months.

Mr Abbott said on Thursday night that he had “read the policy” the night before, though “quickly, it has to be said”. “I'm sorry that it was poorly worded but that's been cleared up". However, Mr Abbott knew enough about the online safety policy to give the Herald Sun an exclusive interview on Wednesday evening about the policy's other bombshell - a new commissioner with the power to jail cyber bullies for up to three months. Loading Labor ministers seized on the bungled policy as proof that perhaps there are other Coalition policies that have been “hidden” from the public.

The Deputy Prime Minister Mr Albanese tweeted: “Libs saying they are sorry their hidden Internet Filter policy slipped out – what other policies and cuts are in bottom drawer”.