The MP Stella Creasy was investigated by children's social care after it received a report from a men's rights activist who was trying to have her children taken away from her. A spokesperson for Leicestershire Police said that the activist was entitled to complain that her 'extremist views' placed her children at risk.
Another example of a person being investigated after a vexatious complaint to the police.
https://www.theguardian.com/politics/2023/apr/29/stella-creasy-targeted-by-troll-who-tried-to-have-her-children-removed-report