The phrase "sex pest" refers to someone who repeatedly behaves in a sexually inappropriate or harassing manner towards others. It is used to describe individuals who make others feel uncomfortable or violate their boundaries. Full definition
They had imposed images of Rupert the bear on a strip by Robert Crumb, a witty, highly regarded writer whose work focuses mostly on an impression of himself as a frenzied sex pest. (politics.co.uk)
Changing their tune AGAIN, Liberal Democrats now say that Rennard was forced to quit as Chief Executive because of sex pest allegations (conservativehome.blogs.com)