At least 1,400 children were subjected to appalling sexual exploitation in Rotherham between 1997 and 2013, a report has found.
Children as young as 11 were raped by multiple perpetrators, abducted, trafficked to other cities in England, beaten and intimidated, it said.
The report, commissioned by Rotherham Borough Council, revealed there had been three previous inquiries.
Council leader Roger Stone said he would step down with immediate effect.
Mr Stone, who has been the leader since 2003, said: "I believe it is only right that as leader I take responsibility for the historic failings described so clearly."
The inquiry team noted fears among council staff of being labelled "racist" if they focused on victims' descriptions of the majority of abusers as "Asian" men.
'Doused in petrol'
Professor Alexis Jay, who wrote the latest report, said there had been "blatant" collective failures by the council's leadership, senior managers had "underplayed" the scale of the problem and South Yorkshire Police had failed to prioritise the issue.
Prof Jay said: "No-one knows the true scale of child sexual exploitation in Rotherham over the years. Our conservative estimate is that approximately 1,400 children were sexually exploited over the full inquiry period, from 1997 to 2013."
Revealing details of the inquiry's findings, Prof Jay said: "It is hard to describe the appalling nature of the abuse that child victims suffered."
The inquiry team found examples of "children who had been doused in petrol and threatened with being set alight, threatened with guns, made to witness brutally violent rapes and threatened they would be next if they told anyone".
Five men from the town were jailed for sexual offences against girls in 2010, but the report said police "regarded many child victims with contempt".
District Commander for Rotherham, Ch Supt Jason Harwin said: "Firstly I'd like to start by offering an unreserved apology to the victims of child sexual exploitation who did not receive the level of service they should be able to expect from their local police force.
"We fully acknowledge our previous failings."
Ch Supt Harwin said the force had "overhauled" the way it dealt with such cases and had successfully prosecuted a number of abusers.
But he admitted: "I accept that our recent successes... will not heal the pain of those victims who have been let down."
The report found: "Several staff described their nervousness about identifying the ethnic origins of perpetrators for fear of being thought as racist; others remembered clear direction from their managers not to do so."
Failures by those charged with protecting children happened despite three reports between 2002 and 2006 which both the council and police were aware of, and "which could not have been clearer in the description of the situation in Rotherham".
Prof Jay said the first of these reports was "effectively suppressed" because senior officers did not believe the data. The other two were ignored, she said.
The inquiry team found that in the early-2000s when a group of professionals attempted to monitor a number of children believed to be at risk, "managers gave little help or support to their efforts".
The report revealed some people at a senior level in the police and children's social care thought the extent of the problem was being "exaggerated".
Prof Jay said: "The authorities involved have a great deal to answer for."
A victim of abuse in Rotherham, who has been called "Isabel" to protect her identity, told BBC Panorama: "I was a child and they should have stepped in.
"No matter what's done now... it's not going to change that it was too late, it should have been stopped and prevented."
James Vincent, BBC Look North
The scale of this report is simply staggering and some of the detail extremely hard to read.
It lays out how Rotherham Council and the police knew about the level of child sexual exploitation in the town, but didn't do anything about it.
They either didn't believe what they were being told, played it down, or were too nervous to act. The failures, the report says, are blatant.
The report estimates 1,400 children were sexually exploited over 16 years, with one young person telling the report's author that gang rape was a usual part of growing up in Rotherham.
The processes for dealing with these crimes have got better in the last four years, but still improvements need to be made.
There were more apologies from the council today but the report's author says they are too late.
Speaking about her abuser, Isabel said: "I think because the police were aware and social services were aware and he knew that and they still didn't stop him it I think it encouraged him.
"It almost became like a game to him. He was untouchable."
Speaking after the publication of the report, Victims' Commissioner Baroness Newlove said: "I'm appalled by the extent of the horrific abuse endured by these vulnerable victims.
"It's deeply distressing how the authorities failed to protect these young people and their voices were not heard.
"Everyone involved needs to take responsibility for the shocking failings that this report has exposed. This must not happen again.
"I want to see every one of these victims getting the right support now and for as long as it takes them to help them on the path to recovery."
Maggie Atkinson, children's commissioner for England, said the number of identified child victims was "largely consistent" with the findings of their own national inquiry into "child sexual exploitation in gangs and groups".
Rotherham council's chief executive, Martin Kimber, said he accepted the report and the recommendations made and apologised to the victims of abuse.
He said: "The report does not make comfortable reading in its account of the horrific experiences of some young people in the past, and I would like to reiterate our sincere apology to those who were let down when they needed help.
"I commissioned this independent review to understand fully what went wrong, why it went wrong and to ensure that the lessons learned in Rotherham mean these mistakes can never happen again.
"The report confirms that our services have improved significantly over the last five years and are stronger today than ever before.
"This is important because it allows me to reassure young people and families that should anyone raise concerns we will take them seriously and provide them with the support they need.
"However, that must not overshadow - and certainly does not excuse - the finding that for a significant amount of time the council and its partners could and should have done more to protect young people from what must be one of the most horrific forms of abuse imaginable."