A learning disability charity is calling on a dating website to remove an "inappropriate, offensive and discriminatory" question from its site.
Mencap has said OkCupid asks users as part of its screening process: "Would the world be a better place if people with low IQs were not allowed to reproduce?"
The charity said the question is offensive towards people with a learning disability and called for an immediate apology.
Amy Clarke, a Mencap spokeswoman - who has a learning disability, said: "I am very upset that OkCupid could ask a question about whether people with a learning disability should be allowed to have children. This is not OK.
"It is shocking and offensive. As by asking the question, they are making it seem like it is OK to say yes which it is not.
"If they had asked the same question about people of different races or sexuality, there would be outrage and it should be the same for people with a learning disability."
She added: "I think OkCupid should apologise immediately for this and remove it from their website. "
Ciara Lawrence, a Mencap campaigner who has a learning disability, has started an online petition which has more than 500 supporters.
She said: "As someone with a learning disability who is married and thinking about maybe having children in the future I find this question inappropriate, offensive and discriminatory.
"It should not matter who you are when you have children, just that you will love them and do everything you can to raise them in the right way."
Ms Lawrence added: "Since I was diagnosed with a learning disability when I was 10, I've been told: 'you will never', 'you can't', 'you won't'. All negative attitudes. It was hard for me to imagine then that I would ever achieve anything I dreamed of in my life.
"However, now I am married, have a great job working at Mencap, and live an independent and happy life.
"I am very lucky that I have the right support around me. However, I know how important it is for people with a learning disability to have positive role models in their life, and be encouraged to fulfil our dreams.
"I think OkCupid should immediately remove the question and apologise for any offence it has caused."
The title of Ms Lawrence's petition is "Tell @OkCupid that discrimination is NOT Ok #NotOkCupid", and on the page she said she was "horrified" when she became aware of the question on the dating site.
OkCupid has been contacted for comment.
A spokesman for OkCupid said: "Our question system is designed to help potential matches understand the interests and values of other users.
"Questions range from mundane to provocative and they specifically allow you to determine your potential compatibility with someone else and to avoid people whose viewpoints you strongly disagree with."