Speaking on Watch What Happens Live! in the US, the 54-year-old actress revealed they have a file called ‘Nutters’ in the office in London.
“And every time, well, particular people send letters - they still send, you know, mail - they have to go into the Nutter file,” Liz said.
She said, however, there was one ‘nutter’ who only stalks two people.
“I don't even know if I'm allowed to say this - but he only stalks two people: I'm one of them and the other is the Queen of England. I probably shouldn't be saying any of this on TV. Take it all back!”
The Royals star - who has 1.4 million followers on Instagram - recently admitted she holds back on social media because she's famous and would prefer to be silly.
“It's a good tool for business but if I wasn't in the public eye I'd probably thoroughly enjoy having a very small private account, followed only by my friends - and then I could be a great deal sillier.
“And I do feel in our very busy lives that it's a brilliant way of keeping in touch; if you bump into someone, you feel like a bit of a stalker really as you know exactly what they've been doing, but I kind of like it.
“It's a force of good unless you're a teenager and do nothing but social media - but I probably spend 10 minutes a day on it."
Elizabeth previously “made a vow” to keep quiet about her personal life.
When asked about her love life, the mother-of-one - who has 17-year-old son Damian with ex-partner Steve Bing - said: “I made a vow a few years ago to keep quiet about my private life for a bit, because I decided I talk too much about it in the past! So I'm not going to answer that, but I will say thank you for asking!”
With reporting by Bang Showbiz.
Got a story tip or just want to get in touch? Email us at email@example.com.