I'm currently in the UK, and at least here I've been told by legal that a negative reference can lead to massive issues in front of an Employment Tribunal, and that it's effectively not worth it when we can just decline to give any reference at all.
On the flip side, a reference has an implicit duty of skill and care to both the former employee and the person asking for the reference, so an overly-positive reference can also lead to legal liability from the person asking for the reference.
On the flip side, a reference has an implicit duty of skill and care to both the former employee and the person asking for the reference, so an overly-positive reference can also lead to legal liability from the person asking for the reference.
In some regulated industries the content and form of references is also regulated as well, for example see pages 11 and 31 of https://www.handbook.fca.org.uk/handbook/SYSC/22.pdf
(None of this is legal advice)