A British woman has told how she was kidnapped as a teenager and held captive for 13 years by a sadistic paedophile who sold the babies she had from him raping her.

Anna Ruston was befriended by an Asian taxi driver in the Midlands who lured her to his home before imprisoning her for more than a decade.

Held in a locked bedroom, she was raped almost every night, eventually escaping after she concocted a plan with a visiting health worker.

But her attacker remains unpunished as she has never felt strong enough to give evidence that could help bring him to justice Now free for 16 years, Ms Ruston - not her real name - has written a book as part of therapy for her experiences, Secret Slave, published on Thursday.

In it, she explains how she was imprisoned when she was just 15 after meeting the man, named Malik, at a taxi rank where she worked, according to the Daily Mirror.

Rejected by her parents growing up, she was befriended by Malik and in 1987 invited to the home he shared with his brothers, their wives, children and his mother to "meet his family for tea".

Malik asked her to stay the night - before storming into her room and branding her a "filthy white s***" whom he would "make his own".

Ms Ruston says he violently raped and abused her - a pattern he would repeat for the next 13 years, eventually allowing his brothers to visit her and prostituting her out to other men.

She said: "I can still see that bedroom, the corner where I would rock in pain. Although after a while I stopped feeling pain, I think my body shut down.

"And I can smell it - the can I used as a toilet, the garlic he reeked of. I got to the point where I didn't know what life was."

Ms Huston described how she clung on to sanity by talking to her late grandmother - and by looking at a small photo of her first boyfriend, Jamie, she hid under a floorboard.

Over the years she became pregnant and had four babies, but each was sold by Malik soon after birth. She said: "I barely held any of my babies, I did not get the chance to be a mother to them."

Ms Ruston tried to escape but became terrified after she was badly beaten for daring to make the attempt, and repeatedly tried to kill herself.

She said she would have eventually succeeded had it not been for a health visitor who helped her escape while the family were distracted.

Finally free, she was again shunned by her mother - who never tried to find her while she was missing - but found happiness with Jamie, who had been in the Army, going on to have four children together.

For years she told him she had moved away after being in hospital with anorexia, only telling him the truth last year.

Ms Ruston said: "He went away for a day, I thought I had lost him, that he would judge me. But he came back and just hugged me."

In such cases of modern-day slavery, police should not always need a victim's evidence to take action, according to Kevin Hyland, the independent anti-slavery commissioner.

He told BBC Radio 4's Today programme: "It doesn't always need a victim to give evidence. Sometimes there's ways of collating evidence without a victim.

"That's why I've been saying continuously and in my annual report to Parliament this year, saying this is serious organised crime and policing needs to use the same techniques, the same level of resources, like it does for other serious and organised crime."