Australia goes to the polls on Saturday to elect a new national government - but the likely winners of the election have just suffered an embarrassing reversal after a day during which they proposed, then withdrew, a plan for a national anti-smut internet filter.

The proposal was contained in a policy document published today, titled The Coalition’s Policy to Enhance Online Safety for Children. "The coalition" refers to Australia's right-of-centre Liberal and National parties, who form a united bloc in Parliament and are likely to win the election. Vulture South has placed the policy document here for your reading pleasure.

We've done so because the policy has since been withdrawn, because it contained the following promise:

We will introduce nationally agreed default safety standards for smartphones and other devices, and internet access services. As has recently been achieved in the United Kingdom, we expect these standards will: involve mobile phone operators installing adult content filters on phones which will be switched on as the default unless the customer proves he or she is at least 18 years of age; and

involve major internet service providers providing home network filters for all new home broadband services, which will be switched on as the default unless the customer specifies otherwise.

The emergence of the policy was a big surprise, because the coalition spent years criticising the incumbent Labor government's past plans for a national internet-access filter, saying that policy was unwelcome state intervention and/or an erosion of free speech.

In an extraordinary reversal, the policy has now been disowned.

This page offers the following explanation:

The Coalition has never supported mandatory internet filtering. Indeed, we have a long record of opposing it. The policy which was issued today was poorly worded and incorrectly indicated that the Coalition supported an “opt out” system of internet filtering for both mobile and fixed line services. That is not our policy and never has been. The correct position is that the Coalition will encourage mobile phone and internet service providers to make available software which parents can choose to install on their own devices to protect their children from inappropriate material. The policy posted online today is being replaced with the correct version.

Malcolm Turnbull, the shadow minister responsible, tweeted to confirm the error.

Here is another link to our correction confirming we oppose a mandatory filter and oppose an opt out filter http://t.co/1SVFNO0sgK — Malcolm Turnbull (@TurnbullMalcolm) September 5, 2013

But efforts to explain away the policy as a mere version-control problem are on thin ice, as at the 26:30 mark of this Soundcloud file Turnbull explains and supports the policy.

No replacement policy has been posted, so at the time of writing it's impossible to say whether another of the withdrawn document's plans - laws to regulate social media - will be taken to the election.

That plan calls for “an effective complaints system, backed by legislation, to get harmful material down fast from large social media sites”.

That measure is a response to outcry caused by a Facebook page listing the number plates of unmarked police cars and such online postings. Australia's also had a national debate of sorts on trolling. The policy is therefore not out of kilter with community sentiment, even if it was not deemed important enough for mention early in the campaign.

It's also unclear how it would be possible to enforce such a law. The likes of Facebook and Twitter operate offices in Australia, but takedown requests could be ignored by their parent American companies.

The policy reversal comes after an election campaign during which Australia's national broadband network has been only a minor issue. Today's government favours a fibre-to-the-premises build, hooking people straight up to the good stuff. The coalition favours fibre-to-the-node, saying it will be faster and cheaper to build. ®