The actress first played Patsy Stone in the sitcom in 1992 and recently reprised the role in this year's Olympics special.
"It was very good fun," Lumley told Metro. "It's 20 years since the first one. It makes us laugh too much to let the characters go.
"It's all up to Jennifer Saunders if there will be more. If she writes a film, I'll be in it."
Asked for people's misconceptions about her, she replied: "That I'm exactly like Patsy. I drink a fraction of what she does and I'm fatter than she is but I'm a bit like her.
"I don't have her vicious language but I adore her. We put some of my experience into her past. She'd been a model in the 1960s who used to hang around with rockers."
Lumley added: "I knew girls like Patsy - Eurotrash figures who didn't seem to belong anywhere but were always immaculately turned out and could be found in Saint-Tropez.
"You could never work out quite how they lived and Patsy was one of those."
