Colin Firth's ex-wife, Livia Firth, has opened up about why she continues to use his surname years after their divorce.

The Italian activist and eco-fashion campaigner explained in an Instagram video on Monday why she still uses the Pride and Prejudice actor's last name on her social media accounts, four years after their split.

She stated that she decided to address the topic after repeatedly being questioned by social media users.

"Many of you ask me, why do I still use the name Livia Firth in my Instagram account?" Livia began in the clip. "First of all, it's very interesting that it's always in an accusatory way. It's never anything different. It's always like, 'Oh, why do you...?' Which always makes me smile."

The 56-year-old went on to explain that she built her professional identity under her married name.

"When I started my social media activity, many, many, many years ago, my (handle) was Livia Firth with the blue tick and verified, and my avatar, in my professional life as an activist, and my career, has always been Livia Firth," she said.

"When I separated, I said, okay, I will move to Livia Giuggioli Firth," the activist continued. "And by the way, Giuggioli, which is my name... I never changed it. Italian women never change their name on documents."

Livia went on to share that she feels a deep connection to the name, which she shares with their sons, Luca, 24, and Matteo, 22.

"I'm incredibly proud of being Giuggioli, and I'm incredibly proud of being Firth," she told the camera. "And I'm a Firth mama. My boys are Firth. And that part will never go away."

Livia noted that she has tried to change her Instagram handle in the past, but found the process "incredibly complicated".

"So that's it. At some point, maybe I'll be able to change it, maybe I'll never change it, and I'll always be Livia Firth even though I'm not married to (Colin) Firth anymore," she said.

Livia and Colin were married from 1997 to 2019.