ITV News Correspondent Martin Geissler reports

Hundreds of child abusers are walking the streets of Manchester because police have failed to investigate claims of abuse, an ITV News investigation has found.

Greater Manchester Police (GMP) has been accused of covering up their failure to act on claims that gangs of Asian men abused young white girls over a 10-year period.

Victims say they have identified offenders but police have been reluctant to act.

Two former detectives have told ITV News that senior officers were not interested in following up allegations because the crime is "difficult to prosecute".

GMP Chief Constable Sir Peter Fahy agreed that child sexual exploitation is a difficult crime to prosecute and claimed his officers "developed a mindset that victims in these sorts of cases would always been unreliable."

The findings come just months after a damning report found at least 1,400 children were subjected to sexual exploitation in Rotherham between 1997 and 2013, with "blatant" collective failings by the council and South Yorkshire Police blamed for the abuse.

Former detective constable Margaret Oliver submitted a report to senior GMP officers more than 10 years ago with details of the abuse allegations.

Oliver said she disclosed the names of victims and offenders to her bosses who took no action.

Oliver - who eventually resigned over the inaction - claims there is a "lack of desire" to investigate abuse, blaming Sir Peter Fahy for the force's failure to tackle the issue.

"There's no lack of evidence, the evidence is there, there is a lack of desire to follow the lines of enquiry," she said.

"Peter Fahy is responsible for GMP. He cannot pretend that he doesn't know what is not being done in relation to the investigation of this kind of crime.

"I told him and I won't be the only person who told him."

She believes if the crime had been taken more seriously a decade ago the problem would not have escalated.

Former detective constable Margaret Oliver speaking to ITV News. Credit: ITV News

Six years after Ms Oliver's initial report, another detective voiced her concern that the problem had spiralled "out of control".

Again, GMP bosses were said to be unwilling to get involved.

"I told them young girls were being abused but they didn't listen or resource the investigation," the officer said.

"They were only interested in target crimes: robbery, burglary and car theft.

"Because this kind of crime is difficult to prosecute and didn't show up quickly on crime figures they weren't interested."

In 2012, nine men were convicted of raping and trafficking young girls as young as 13 in Rochdale.

However ITV News has been told GMP has files full of further names, evidence and statements from victims but no suspects have been charged.

Several police officers, who worked very closely to these investigations, say they are "gravely concerned" by the force's apparent inability to investigate the crimes effectively.

The failure to stop the abuse of young girls in Rochdale is the subject of a major internal investigation at GMP, but the results of that report are yet to be delivered two years on.

In a letter obtained by ITV News, a third officer claims there is a "cover-up" within the force.

He says the report has been re-written on nine separate occasions to water down the apparent failings and to distance senior officers from the probe.

Simon Danczuk, MP for Rochdale, said officers have approached him with concerns over the failure to prosecute alleged rapists.

"It's my view that there are rapists out there that have raped young girls in and around Rochdale, in and around greater Manchester and that the police aren't effectively taking prosecutions against them.

"And I reached that conclusion by the fact that I have police officers coming to me and they are raising concerns."

Addressing the claims, Sir Peter Fahy said: "We must try and do everything we can to contain these people, to get people arrested, to get people convicted, but we are misleading the public if we think absolutely police can solve this problem.

Sir Peter Fahy speaking to ITV News' Martin Geissler. Credit: ITV News

"We made mistakes in the past where some of our officers developed a mindset that victims in these sorts of cases would always been unreliable, and I think that was also a mindset which developed among prosecutors as well.

Asked whether that mindset had changed, Fahy replied: "It has changed but what hasn't changed is the courts system."

Fahy said GMP had to look at the issue in a "much broader way" to stop people abusing, adding: "We will look at people who are abusers and say even if we can't get them for this particular offence, we will try and hit them with anything else we can even - if it's their taxi licence, the shop they run or if they're involved in any other form of criminality."

Asked whether convicting people who rape children of less serious crimes was good enough, Fahy said: "If that's the only thing we can get them for, then that's what we have to get them for."