It doesn't necessarily have to be lies, although truth is a possible defense - but there are issues around parliamentary privilege when politicians sue where it

It doesn't necessarily have to be lies, although truth is a possible defense - but there are issues around parliamentary privilege when politicians sue where it might not be possible for the defendant to mount a truth defence even if it's on the public record that they said something! Our defamation laws are really screwed up - basically, you need to prove that you didn't defame somebody instead of the burden of proof being on the plaintiff to prove it, and you need to have massively deep pockets to sue for defamation (you will likely part with hundreds of thousands of dollars, unless you can get costs awarded - not really anything most 'any other member of the public' can actually do), and you need the same kind of cash to successfully fight somebody suing for defamation against you. It's basically a war of who can pay for the best lawyers. The internet comedian Friendlyjordies managed to settle very favourabliy because he managed to crowdfund literally a million dollars to fight when John Barilaio sued him. Otherwise that wouldn't have been possible for him to even think about fighting it.