David Cameron has been accused of double standards after announcing a crackdown on web porn - but refusing to condemn Page 3.
The Prime Minister wants all households to have to 'opt in' if they want to be able to view pornography on the internet, saying he wanted Britain to be a place "where children are allowed to be children".
He said the internet was free of the controls that exist on 'top-shelf' magazines or adult films.
This led to questions about pictures of topless women on Page 3 of The Sun.
Cameron acknowledged he had not made his point effectively when asked in The Commons by Green MP Caroline Lucas in June.
Asked about the risk of children seeing the images in the newspaper, he told BBC Radio 4's Woman's Hour: "We have to always ask the question: where should we regulate and where shouldn't we regulate?
"On this one, I think it's probably better to leave it to the consumer rather than regulate."
The growing No More Page 3 campaign is aiming to persuade The Sun to drop its traditional daily topless young woman pictures.
In his speech, Cameron said: "Children can’t go into the shops or the cinema and buy things meant for adults or have adult experiences – we rightly regulate to protect them.
"But when it comes to the internet, in the balance between freedom and responsibility, we have neglected our responsibility to our children."
Laura Bates, founder of the Everyday Sexism project, said Cameron was "missing the point" on Page 3.
She said: "The No More Page 3 campaign isn't asking for a ban - they're asking the editor of one of our largest newspapers to rethink the decision to display a picture of a young, airbrushed woman with her breasts out as the largest image and symbol of women in the paper day in, day out."