Singer Nicola Roberts has accused the Government of failing young women by not cracking down on sexting in schools.
The former Girls Aloud star, who is an ambassador for children's charity Barnardo's, said she had heard many "heartbreaking" stories of girls who have fallen victim to online predators.
But while children are warned not to talk to strangers online, the pressures they face from classmates to send naked pictures is often ignored, she warned.
Writing in The Times, the singer, 30, said: "Sexting and child sexual exploitation are serious problems that David Cameron and his Government are simply not addressing."
She called for lessons in personal, social and health education (PSHE) to be made compulsory to help teenagers "navigate their way through society".
She added: "It infuriates me to see the Prime Minister treat this issue with such a lack of common sense.
"And I don't understand why the Education Secretary Nicky Morgan isn't publicly backing this change to the status of PSHE lessons.
"I've read lots of social media posts from Mrs Morgan in which she tries to empower women. And yet she won't fight for an education that keeps women and girls safe."