In today's Observer, columnist Jonathan Bouquet mentions Jon Snow on Channel 4 News while interviewing Jacob Rees Mogg, having used the expression to queer the pudding. Bouquet refers to it as a "new phrase", to which Rees Mogg is said to have "cocked an eyebrow".
I am quite certain I have heard it, and that it means "to introduce unnecessary complications and confusion to an issue". But I cannot find a reference to it anywhere on line. The only response Google gives me is a reference back to Bouquet's article.
Please would someone confirm that I am not imagining things when I say it is a well-known saying, perhaps dated, but certainly in 20th century use.