DH is a well-informed employer in this regard. He says go to your employer. Tell them that it is an issue, and if they don't make it stop they will be liable when you sue them.
He suggests your employers take legal advice, who will advise that they will neeed to make this stop. He says there is very clear legislation on this issue look here
the relevant part is this:
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Harassment
You have the right not to be harassed or made fun of at work or in a work-related setting (eg an office party). Harassment means offensive or intimidating behaviour - sexist language or racial abuse, which aims to humiliate, undermine or injure its target or has that effect. (my italics) For example, allowing displays or distribution of sexually explicit material or giving someone a potentially offensive nickname.
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Basically, if you, or anyone who hears it are offended by something someone says, your employer must take it seriously if a complaint is made. Also, if they penalise you for complaining, then it is victimisation and they can be fined for it.
He also says to advise you to make your complaint in writing (keep a copy!) and ask for a response. Basically, if your employer fails to stop this they are condoning the abuse and are opening themselves to a hefty fine.