The singer Rihanna was last night accused of "sanctioning" domestic violence after she conceded she still feels "protective" towards an ex-boyfriend who was charged with assaulting her three years ago.

In an interview to be broadcast in the US tonight, Rihanna insisted the rapper Chris Brown "made a mistake" and "needed help" when, according to police reports, he punched her in the face, smashed her head against a car window and bit her following an argument on the eve of the Grammys in 2009.

Charities last night criticised her stance. One said she was in danger of "reducing savage attacks to the seriousness reserved for kiss-and-make-up stories in glossy magazines"; while another called for an end to "sticking-plaster policies" in pop culture's attitudes towards domestic violence.

Erin Pizzey, the campaigner who pioneered aid for abused women by setting up Britain's first refuge centre for victims, added: "This sends out a very dangerous message to teenagers that roller-coaster relationships with violence-prone personalities are edgy and exciting. They're not. The relationship is toxic and unhealthy. Both are in need of help and that is the message that young people should be receiving."

In the interview with Oprah Winfrey, Rihanna said that the assault had left her in "a weird, confusing space". Conceding to still harbouring feelings for her former boyfriend, she added: "I lost my best friend – like everything I knew switched in a night, and I couldn't control that. He made that mistake because he needed help. Everybody's gonna say he's a monster without looking at the source. I was more concerned about him."