The Great British Bake Off star, who's a Christian, says she'd want her children to help her die if she 'lost her marbles'.
Her comments come as the House of Lords prepares to scrutinise the Assisted Dying Bill brought forward by Lord Falconer.
His plans would allow terminally ill people to end their own lives.
Alistair Thompson from Care Not Killing, which represents a number of Christian and non religious charities, told Premier's News Hour: "Mary Berry says that she's in favour of changing the law because she doesn't want to feel like a burden.
"What about someone who doesn't have the means and support that she has? What about elderly people who feel that they are using up the inheritance of their loved ones?
"This is why they might feel pressured into ending their lives."
Speaking to the Radio Times Berry said: "I have no desire to be a centenarian. I think 90 is a great time. You've had a good innings.
"You have to deal with the cards that have been dealt, of course, but I don't think very old age, if you haven't got your marbles, can be very nice.
"My mother was in very good health until the last few months. And health is key, isn't it?
"But I would love my children to be able to give me a pill, although of course I do understand that could be abused."
Hear more from Care Not Killing's Alistair Thompson speaking on the News Hour: