'It is a lie': Bill Shorten targets Liberals for death tax 'fake news' on Facebook

Opposition Leader Bill Shorten has hit out at the Coalition for a case of "fake news" being spread on social media, saying his opponents should be ashamed for mounting a scare campaign about a tax on inheritances.

The opposition has demanded Facebook remove material being shared on its platform that incorrectly claims Labor and the Greens have signed a secret agreement to introduce a 40 per cent "death tax".

Opposition Leader Bill Shorten speaking in Melbourne on Saturday. Credit: AAP

The content, which has been shared in posts and messages, links to a media release on Treasurer Josh Frydenberg's website that argues an inheritance tax under Labor is "not out of the question" because the idea has previously been favoured by opposition frontbencher and economist Andrew Leigh and the union movement.

While the Liberal Party has denied being behind the Facebook content, Prime Minister Scott Morrison publicly speculated on Saturday that there was a secret Labor-Greens deal and whether "death taxes" were involved.

Mr Morrison said "it sounds to me that he has struck a deal with the Greens" and questioned what the terms would be.

"What is that deal with the Greens? The Greens are up for death taxes. Even Andrew Leigh is up for death taxes, let alone the union movement," he said.

"What is the deal that Bill Shorten has with the Greens to get all of his taxes through and to get all of his carbon abatement policies, emissions reduction policies, which he won't even explain to the Australian people."

Speaking in Melbourne, Mr Shorten again ruled out introducing an inheritance tax and said he had predicted in January that the "desperate" Coalition might try to create a "ridiculous death tax scare" ahead of the election.

"They did exactly that. It is a lie. It is a lie. It is a lie. And I think the Liberal Party need to be ashamed of themselves using low-rent, American-style fake news which is actually a lie and then trying to scare different communities in Australia," he said.

I think the Liberal Party need to be ashamed of themselves using low-rent, American-style fake news.

Bill Shorten, Opposition Leader

Labor's campaign headquarters has written to Facebook warning that the proliferation of the posts could taint the election, urging the platform to investigate and remove the material.

"I would like to raise serious concerns about a number of apparent fake news posts about 'Labor's death tax' circulating on Facebook very rapidly over the past 12 hours and its possible implications for the Australian federal election," the letter states.