A police probe into the alleged crimes has gone dormant, but the UK's former top child abuse investigator has called for detectives to "double down" on the case after examining a thousand pages of evidence.
sky news about allegations against man a, including one who claims primary school children were targeted.
"If they need additional evidence, then go out and get it," Mr Gamble said of Humberside Police.
"We need to declare war on this type of behaviour, we need to say it is a priority.
"It's not just about exploitation, it is about rape by appointment."
In a series of reports this week, Sky News will meet the alleged victims and examine some of the evidence provided.
sarah ( not her real name ) says at the age of 13 in a block of flats.
"I 'll never forget that girl I saw sat there in a primary school uniform, probably eight or nine years old.
"She was there with her sister, who was a little bit older.
Public faith in police investigations into sexual abuse cases is running low after a report earlier this year found fewer than 2 % of reported rapes led to charges.
The police arrested 34 suspects and say they did digital searches on 150 devices seized, and that phone records did not provide supporting evidence.
The women who spoke to Sky News provided evidence including diaries with accounts of grooming, photos of the bruising and strangulation marks that they say were caused by the men.
so, it's not just 'he said, she said.
A grooming gang said to be operating in Hull has been targeting girls as young as 'eight or nine years old ', it has been reported.
Sky News has been examining evidence provided by one young woman called Sarah ( not her real name ).
She told Sky News – whose report the police have said contains inaccuracies – the abuse started after two men showered her with gifts, before one of them eventually forced himself on her saying : 'It's time for you to pay for all the things we ’ ve given you ’.
But despite naming her attackers and providing documents which she says backs up the claims, the operation was wound down after two years with no charges brought against any of the more than 30 people arrested.
It includes photographs of texts from a man threatening to kill her if she does not come immediately and have sex with a number of men.
Speaking about the threatening text, former chief police officer Jim Gamble said : "Number one is he's committed a criminal offence because that's a threat to murder, and the Offences Against the Person Act makes that a crime.
however, humberside police say they did not reach the evidence threshold to bring the case to court.
detective chief inspector rebecca dickinson told sky news : "( with ) a text message in relation to a threat, which would have got them ‘ over that line ’.
Humberside Police Detective Chief Superintendent, Phillip Ward said : "Operation Marksman has been an intensive two-year investigation into reported child sexual exploitation in Hull.
He went on : 'Despite two years of intensive investigation, analysis and examination, we share the disappointment and frustration that we have been unable to identify sufficient evidence to corroborate or support the accounts given to us by the victims.
'as a result, we have been unable to meet the crown prosecution service's evidential threshold for us to formally charge anyone in relation to operation marksman.
'critically the investigation found no evidence of organised child exploitation in any part of our community, either geographically or through ethnicity.
"I would like to reiterate while current lines of enquiry have been exhausted, we will never fully close this investigation and I urge anyone with new information to get in touch with us as a priority.
'we will investigate all information provided to us.
"we encourage anyone that has been a victim of sexual abuse of any kind to get in touch using the non-emergency line, 101.
You will be treated seriously, you will be provided appropriate support from the police and partner agencies and we will do everything we can to investigate the case fully and bring those that commit such crimes, to justice."
A gang of child abusers is allegedly at large in the city of Hull.
"I think I was raped by around 150 men over the three-year period, sometimes 10 or 11 men wanted to rape me per day."
I remember her screaming in that bedroom."
she claims that in her early teenage years, she was threatened with being buried alive or set on fire if she did not return regularly to a flat to be raped by the men.
"But what you do see there is the coercive control.
you see the fact that the predator is so confident in their ability, their level of competence at controlling these young people, that they don't even try and hide it or mask it.
"i'd be surprised if they 're not able to pass the evidential threshold ... because what you do have is significant levels of corroboration."
By corroboration, he is referring to testimony and evidence of the other young women in this case.
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the girl was taken to hospital and had suffered scratches and a cut.
cowap told the court that he would, in future, muzzle the dog all the time and have it on a lead.
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