I’m sorry you’re dealing with this. It sounds awful.

My take: send him a note (email) saying you’d like him to stop asking you out. Also, no more bringing up the other times he’s pursued you. Be clear that you don’t want this mentioned at all.

Explain that the jokes are putting you in an uncomfortable position, and that you’d rather go back to being cordial, respectful colleagues who can enjoy each other’s company. If he needs space to get over it, you’ll understand.

Putting things in writing is good.

Hopefully he’ll let you know he gets it. And if he says bad things about you to other people at that point … well, you can’t control that – and that’ll say more about him.

If he doesn’t respect your boundary, you can take the issue to a manager with the note you sent. You don’t want work to get more uncomfortable and messy, but if he can’t follow your rules, the next steps have to be bigger.

But let’s hope he gets the point. 

Another thing: I understand why you lied about not wanting to date someone from work, but you might decide to date a colleague eventually. Then things could get weird with everyone. It’s kind of you to want to soften a rejection by telling a lie, but dishonesty can make things more confusing.

He’s been trying to convince you to break your dating rule, but that rule is fiction. He should know you don’t want to date him, specifically.