Emma star Stevenson, 53, is convinced the acting community is biased towards women under 30 - insisting Dame Helen Mirren and Kim Cattrall are the only stars who can escape playing "mother" roles.
She says, "When women's parts are being written, they are more and more for under-30s who are nubile and beautiful. Actresses over 40 are finding very little happening.
"It's frustrating. As you go on in your life you get more complex and have more life experience, but lots of writers don't think that way.
"The fact that we can only cite singularly people like Kim Cattrall and Helen Mirren who play roles which aren't mothers is a symptom of the situation. The roles get diminished, smaller and typecast. All the executives are male. They are chasing young skirt."
And 67-year-old Jones believes ageism in the industry is prompting an increasing number of mature women to go under the knife.
The Bridget Jones's Diary star adds, "I've been incredibly lucky as an older actress, but I am an exception to the rule. We still have our marbles and our energies and experiences but the jobs and roles aren't there.
"This ageist thing is very worrying because women think they have to keep looking young. I look at cosmetic surgery and I find it very sad because I love mature women who look as if they have lived, but there's an anxiety about having to pretend to be younger than you are."