Scott Mitchell said the 82-year-old former EastEnders star left the couple’s home in mid-July.
Dame Barbara was diagnosed with Alzheimer’s in 2014 and her condition has worsened during lockdown.
Speaking to The Sun newspaper, her 57-year-old husband said: “I feel I’m on an emotional rollercoaster. I walk around, trying to keep busy, then burst in to tears. It feels like a bereavement.
“It’s always been my biggest fear, that one day I would have to take her somewhere and she’d be thinking, ‘Why would he do this to me?’
“That fear has become a reality. It’s something I never wanted.”
Mitchell, Dame Barbara’s husband of 20 years, said she moved to a care home in London and he has decorated her room to make it as welcoming as possible.
He has put up family pictures as well as a photograph of the actress receiving her damehood from the Queen and a snap of her with Paul O’Grady and Cilla Black at the Royal Variety Performance.
Speaking of the day he left Dame Barbara at the home, Mitchell said: “I’ll never forget the feeling of emptiness. I felt sick in the pit of my stomach that I’d left her. I still feel like that.
“By the time I got home and went to bed, I just felt desperately sad. It’s been 27 years since we met and we spent so much of that time in each other’s company. It feels like another chapter has gone.”
Dame Barbara was diagnosed with Alzheimer’s six years ago and made the news public in 2018.
Both Dame Barbara and her husband have campaigned to raise awareness of the illness, which is most common in people over the age of 65.