Vice Chancellor Heinz-Christian Strache, head of the far-right Freedom Party, made the accusation on Facebook.
He has long accused the ORF of left-wing bias and said he wants to abolish the licence fee that supports it.
The news presenter involved, Armin Wolf, is also suing Mr Strache.
He says no politician has accused him of lying before.
The row started two weeks ago when Mr Strache posted a picture on Facebook of Mr Wolf with the words: "There is a place where lies become news. That place is ORF."
He later argued that because he had used the word "Satire!" as a caption on the posting it was clearly not to be taken seriously.
But ORF and Mr Wolf were not appeased.
"Vice Chancellor Strache accused ORF, by doctoring ORF advertising material, of spreading fake news, lies and propaganda in all its media," said ORF Director General Alexander Wrabetz in a statement.
He said the text was "libellous and damaging to (ORF's) reputation".
ORF said it was also taking legal action against Facebook for not deleting Mr Strache's post.
Austrian President Alexander Van der Bellen has condemned Mr Strache's remarks.
The Freedom Party is the junior partner in a coalition with Chancellor Sebastian Kurz's conservatives.
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