Emily Blunt and John Krasinski. (WENN.COM)

Emily Blunt refuses to reveal the intimacies of her relationship with actor fiance John Krasinski - because she has learned her lesson after opening up about her romance with ex-boyfriend Michael Buble.

The Devil Wears Prada actress dated the Canadian singer for three years, and openly talked about their relationship while they were together.

But after they split in 2008, the actress admitted she regretted revealing the intimate details of their romance to the press.

She is now engaged to The Office star Krasinski, who proposed last August.

But Blunt remains silent about her man in interviews - insisting celebrities must maintain a "dual existence" in a bid to keep their love lives out of the tabloids.

She tells Popeater.com, "Don't be a Chatty Cathy about (the relationship) - I think that's the secret.

"You have to have a dual existence... You have the acting side of it and the business life... and then you have your private life and your downtime. You have to make that divide, and make it clear to you."