Myleene Klass has urged the public to help find a street robber who tried to snatch her sister's handbag and dragged her pensioner mother on the ground as she tried to stop him.
The attempted robbery happened as her sister Jessie, 33, and 67-year-old mother Magdalena were walking in Whittingham Road, Wood Green, in north London, at around 9.20pm on January 7.
He eventually fled empty-handed but only after Klass's sister was assaulted as she resisted the attack, Scotland Yard said.
A police spokesman said: "The male assaulted her, he dragged her to the ground, pulling her along the pavement and continued to assault her. A 67-year-old woman tried to hold on to the victim and was also dragged along during the violent struggle."
Speaking as north London's Haringey police released CCTV stills of a suspect they are keen to trace, Klass said: "I am horrified by what happened to my mum and sister, as anyone would be if this were a member of their own family, and I urge any person that knows anything or can help in any way to please come forward."
Her sister received minor injuries but did not require hospital treatment and no items were taken. Both women were very distressed by the incident, Scotland Yard said. No arrests have been made.
Detective Constable Pat Dunne said: "This was a terrifying attack on two women on a main road. I'm confident someone will be able to identify the suspect pictured in the images released today."
Witnesses and people with information can contact police on the incident hotline 0203 2763070 or crime stoppers on 0800 555 11.