It became known as Mark Zuckerberg's "apology tour" — a string of contrite appearances before politicians in Washington and Brussels last year, where the Facebook founder vowed to stop the spread of fake news and voter manipulation on his platform.

Key points: The AEC raised concerns with Facebook over sponsored political ads

The AEC raised concerns with Facebook over sponsored political ads Documents obtained by the ABC show Facebook unwilling to provide details behind possibly illegal posts

Documents obtained by the ABC show Facebook unwilling to provide details behind possibly illegal posts Australians interested in Donald Trump were targeted with ads attacking The Greens and Get Up!

"From now on, every advertiser who wants to run political or issue ads will need to be authorised. To get authorised, advertisers will need to confirm their identity and location," told a US Senate committee in April last year.

"We're starting in the US and expanding to the rest of the world in the coming months."

But internal documents obtained by the ABC reveal a very different message coming from Facebook's Australian headquarters.

Just months after Mr Zuckerberg's testimony, the social media giant was pushing back against efforts by the Australian Electoral Commission (AEC) to identify the users behind potentially illegal political ads.

Almost a year later and on the eve of the federal election, Facebook is yet to bring its new authorisation rules for political ads to Australia.

Facebook chief executive Mark Zuckerberg fronted the US Senate Commerce and Judiciary Committee in April 2018. ( Reuters: Aaron P. Bernstein )

The threat of political interference on social media during the campaign has become so serious that the AEC has warned Facebook and Twitter they face court-ordered injunctions if they cannot remove illegal political ads.

Facebook's attitude revealed in FOI documents

The surprisingly informal, somewhat haphazard, relationship between the AEC and Facebook is laid bare in a series of emails and other documents obtained as part of freedom of information application.

The AEC contacted Facebook after it became concerned about a mysterious group called Hands Off Our Democracy, which was paying for sponsored posts attacking left-wing groups and political parties last year.

This sponsored post caught the attention of the AEC due to it failing to disclose who paid for the advertisement on Facebook. ( Supplied )

On July 4 last year, AEC lawyer Andrew Johnson told Facebook's senior counsel Sophie Malloch in an email that the commission had received a complaint regarding Hands Off Our Democracy's Facebook page, which "does not contain an authorisation to indicate who is responsible for the page".

"Can you please advise who is responsible for the Hands Off Our Democracy Page and their contact details," Mr Johnson wrote.

"If this is not possible, we ask that this Facebook page is blocked or removed until it complies with the authorisation requirements in the Electoral Act."

Under changes introduced to the act last year, all online advertisements that deal with electoral matters must include the name and address of a person responsible for the ad.

The Hands Off Our Democracy Facebook page carried no information about who was behind the group, and a post on its own website made clear that its members had chosen to remain anonymous.

Facebook initially appeared willing to help the AEC make sure those ads carried the required authorisation, but did not provide the AEC with any information about who was behind the page.

"I passed this along to our govt case work team as an urgent escalation to see what can be done about this page, including whether it can be geoblocked until an authorisation is included," Ms Malloch wrote in her reply to Mr Johnson.

But five days later, Ms Malloch sent a follow-up email, brushing aside the AEC's concerns.

Emails obtained by the ABC under FOI show a difference of opinion in exchanges between the AEC and Facebook. ( Supplied )

"The Hands Off Democracy page appears to contain organic user content, rather than advertising paid for through Facebook's online advertising process, and does not seem to require authorisation," she wrote.

"If you have a different view please let me know."

Mr Johnson responded by sending a screenshot of a sponsored post by Hands Off Our Democracy, which attacked The Greens and the activist group GetUp! and did not include the correct authorisation.

"The Australian Greens and GetUp! are against laws strengthening our national security. Why? BECAUSE THEY WANT THEIR FOREIGN DONATIONS," the ad reads.

Mr Johnson said the screenshot indicated the group's page "has (or did have) sponsored content".

A series of email exchanges between Mr Johnson and Ms Malloch followed, in which the pair discussed whether the page should carry authorisation information.

But before the AEC's concerns were addressed, Hands Off Our Democracy's page disappeared from Facebook.

If you have been targeted by unusual political messages in the lead up to the federal election, show us what you're seeing. Email hiddencampaign@abc.net.au

Finally, on August 14 — more than a month after the matter was raised with Facebook — Ms Malloch conceded that the page was indeed paying for ads.

"It appears that this page was removed by the administrator before we could take any action, but yes you are correct — the "sponsored" posts were ads," she wrote.

Facebook said the reason it did not take further steps is because when it reviewed the page on July 4, it no longer contained paid ads.

Therefore, it did not appear to be in breach of any electoral rules.

"We have a productive relationship with the Australian Electoral Commission and have an established dedicated escalation path for the AEC to notify us of any advertising content that violates the Electoral Act," Facebook said in a statement to the ABC.

"When this happens, we will block the content out of respect for local law."

The sponsored post attacking Get Up! and The Greens had received hundreds of likes and comments and had been shared widely prior to its disappearance from Facebook.

Australians 'interested in Donald Trump' targeted with ads

Some ads were targeted toward Australians 'interested in Donald Trump.' ( Supplied )

Facebook has been the subject of international condemnation for its role in allowing subversive political messaging to proliferate across its platform, most notably during the 2016 US presidential election.

Its relevance in shaping political opinion has only been underscored by major and fringe Australian political parties increasingly spending up on sponsored posts and tailored social media campaigns.

Screenshots of some from the Hands Off Democracy page show that Australian users who are interested in right-wing politics and Donald Trump were among those targeted by sponsored posts.

Michael Jensen, a political communication and technology researcher at The University of Canberra who has viewed the exchanges between Facebook and the AEC, said the episode demonstrates the social media giant's reluctance to hand over users' details to authorities — even when those users, and Facebook, could be in breach of the law.

"I was disappointed there was, for example, over a month gap between the initial registration of a complaint and finally Facebook's legal team admitting that it was something other than what they were talking about," he said.

"They have a definite preference for following their own rules."

Concerns build ahead of federal election

In the weeks after the Hands Off Our Democracy episode, the AEC sought to create a formal set of protocols for social media companies to deal with potentially illegal political ads.

The Hands Off Democracy page also sponsored conspiracy posts about US billionaire George Soros. ( Supplied )

It sent Facebook and Twitter a document titled "Authorisation of electoral communications on social media scenarios," which makes clear that it expects Facebook and Twitter to respond to its notifications of illegal ads by either removing or blocking the post, or by passing on the details of the creator of the ad to the AEC.

The document said if Facebook and Twitter could not comply with those expectations, then the AEC may go to court to get an injunction against the them, or the user responsible.

Last week, Twitter announced a range of new disclosure rules it said will increase the transparency of political advertising on its platform.

In a statement to the ABC, the AEC said both Twitter and Facebook "have been broadly complying with the document they received last year".

But Dr Jensen said it would be unlikely the AEC's proposed protocols would be effective, even if Twitter and Facebook agreed to them.

"We live in a world where people who perpetrate illegal and covert acts using Facebook can move at quite rapid speeds," he said.

"If it's going to take a month to finally get Facebook to recognise that there is a problem with a particular ad, then it's a completely ineffective mechanism to deal with this."

A scathing UK parliamentary report into Facebook last week called for an independent regulator to monitor content on social media platforms.

Dr Jensen said given the overwhelming volume of advertising posted on social media every day, it would be difficult for an Australian government to police political advertising without the cooperation of Facebook and Twitter.

Facebook said it will make an announcement on political advertising rules after the federal election is called.