The family of a “lovely” 13-year-old girl who claims to have been groomed for sex by Asian men in Rotherham were so afraid of her alleged abusers that they moved to Spain after their complaints to the police, social services, their MP and the home secretary went unresolved, a court has heard.

The girl, who cannot be named, is the main complainant in the trial of eight men from the South Yorkshire town who allegedly groomed and sexually exploited three underage girls between 1999 and 2003.

Now 27 and a campaigner against child sexual exploitation, she claims her abusers threatened to “gang rape” her mother if she did not submit to their sexual abuse, which took place largely in an alley behind a branch of Boots in Rotherham town centre, in a local park and in bushes near a museum, Sheffield crown court heard on Tuesday.

She claims that Sageer Hussain, 30, first raped her behind Boots when she was 13 and later called her a “white slag” when she tried and failed to stop him. She told police that the first and second time he raped her, between 1 January and 4 April 2003, he told her to scream so that his friends, waiting nearby, would know to come and watch.

She claims that on another occasion she was driven to Rotherham’s Clifton Park by Hussain’s cousin, Mohammed Whied, who sat on the car bonnet watching while Hussain raped her inside. On a further occasion, Hussain allegedly raped her in bushes near the museum, calling her “a big baby” when she protested, then flicking cigarette ash in her hair, Michelle Colborne QC, prosecuting, told the jury. A few days later he punched her in the face and threatened her with a crowbar and set light to an aerosol in her face, the barrister said.

The girl told her mother what had happened and gave a statement to police alleging that various men had raped her, including Hussain. A medical examination in April 2013 recorded bruises to her thighs and bottom, but she quickly withdrew the allegations and no charges were brought. Ten years later she reported the abuse to police again, saying she had been threatened by the men at the time. “For example, they threatened they would gang rape her mother. They would drive around the estate where she lived to make sure they were serious,” Colborne told the jury.

The girl’s parents sought help from social services and the police, writing to their MP and the then home secretary, David Blunkett, who was a Sheffield MP at the time. They had a panic alarm installed in their house and eventually moved to Spain to get away, the court heard.

Her mother later told police how she watched her child turn from “a loving, lovely girl to one she described as ‘horrible’ and she was powerless to control”, Colborne told the jury. She asked: “What causes a perfectly lovely child to go from that state to a life of deceit and fear?” Hussain had subtly groomed the girl with cigarettes, alcohol and cannabis, she said.

The complainant now campaigned against child sexual exploitation, the jury was told. She ha has also written a book about her experiences, given evidence to the home affairs select committee and appeared in a Channel 4 programme called Britain’s Sex Gangs.

Hussain’s older brother, Basharat Hussain, 40, is also accused of repeatedly sexually assaulting the girl during the same period. Another of their cousins, Asif Ali, is accused of raping her too, along with friends Ishtiaq Khaliq, now 33, Waleed Ali, 34, and Masoued Malik, 32. Malik is also accused of false imprisonment and conspiring to indecently assault her when she was 14, along with Naeem Rafiq, 33, in a house in Woodside Walk in Rotherham.

Two further complainants came forward earlier this year to accuse Khaliq of indecently assault on various occasions between August 1999 and December 2001.

The men deny all the charges against them. The case continues.