Shadow foreign secretary Emily Thornberry has criticised the Mr Men and Little Miss books, saying they imply women are "less".
Discussing a university study which found Roger Hargreaves stories portray the women as less powerful and play to gender stereotypes, she said she would prefer the female characters were referred to as Ms.
She told ITV's Good Morning Britain: "I don't like this thing about being little.
"I think that's what my problem with the Mr Men books is.
"So why is it that you have Mr Men, and then Little Miss? Do you see what I mean? There is something about women being less."
Asked by host Piers Morgan which character in the series she identified with, she said: "If it was Ms, I don't have any problem with being Ms Trouble."
Morgan criticised the study, which was presented by the University of Lincoln at the British Psychological Society's annual conference and reported by the Daily Mail, saying: "Why do people bother with these things?
"Imagine taking the Mr Men books seriously, thinking 'I know what I'm going to do, I'm going to do a very in-depth deep dive investigative survey into why Mr Men is sexist'."