Vulnerable women are most likely being "extensively" abused across the UK and ministers need to urgently review sex exploitation laws, a report says.
He said exploitation was not being recognised in adults.
The operation identified about 700 victims in total across the Northumbria Police area, 108 in Newcastle.
The government said it would "look carefully" at Mr Spicer's 33 recommendations, which also included a need for research into the cultural background of abusers, many of whom in the case of Sanctuary were from a "predominantly Asian or British Minority Ethnic culture or background".
Mr Spicer, who carried out the serious case review for the Newcastle Safeguarding Adults and Children Boards, said it was clear "adults were being targeted, groomed and exploited" as well as children.
But he said authorities did not have the powers to intervene with adults to stop them "making bad choices" or forming "inappropriate relationships".
He said: "Vulnerability is not determined by age and it is likely that extensive abuse of vulnerable adults is taking place across the country unrecognised."
Operation Sanctuary started in 2014 after a 21-year-old woman with a learning disability told police she had been a victim of sexual exploitation over a long period.
Further reports from two 19-year-old women "confirmed" sexual exploitation was a much larger problem in Newcastle "than previously recognised".
Mr Spicer said the operation had proved successful but it was only when Northumbria Police and other agencies like Newcastle City Council started looking for the issue they found it.
He also said the government needs to research the "profiles, motivations and cultural and background influences of perpetrators of sexual exploitation".
In the Newcastle case, most of the men were British-born but all came from Bangladeshi, Pakistani, Indian, Iraqi, Iranian or Turkish communities.
The Quillam Foundation think tank, which focuses on counter-extremism, said 84% of the 264 offenders it looked at, who were convicted of gang grooming between 2005 and 2017, were of south Asian heritage.
Mr Spicer said the perpetrator he spoke to "displayed no regret" and "spoke in a derogatory manner about a lack of morals in British girls".
The report noted that there was no evidence that police and other agencies had been reluctant to investigate amid "misplaced" concerns over political correctness or allegations of racism.
Mr Spicer also said confidentiality systems in sexual health services should be reviewed as a lack of information-sharing meant no-one spotted victims who went to multiple clinics.
Medical professionals such as pharmacists should also be trained to spot signs of abuse, he said.
Mr Spicer was also critical of the ordeal of victims giving evidence in court saying several complained it caused "lasting serious mental health problems".
As well as reviewing the way victims are treated during trials, Mr Spicer also said the terminology of charges should be changed to avoid causing further distress.
This was after victims complained the charge of "inciting prostitution" labelled them as prostitutes.
The report also looked at exploitation of boys and men but said it was "complex and hidden" and operated differently to female victims.
Mr Spicer said: "The low incidence of identified cases is likely to be a significant under-representation of the abuse occurring."
He also said it was not within the scope of his review to investigate Northumbria Police's £10,000 payment to a convicted child rapist who acted as an informant.
A government spokesman said: "These are abhorrent crimes that have had a devastating impact on the lives of the victims involved."
Changing Lives, a charity which supports victims of sexual exploitation including 33 associated with Operation Sanctuary, praised the report
Director Laura Seebohm said the trauma "cannot be underestimated" and she welcomed the recommendations for "national debate, review and guidance".
Vida Morris of Newcastle's adults safeguarding board said she was "profoundly and deeply sorry for the emotional and physical trauma" the victims suffered.
She said the women had been "brave beyond belief" and thanks to them Newcastle was "without a doubt a safer place".
Northumbria police and crime commissioner Vera Baird declined to be interviewed.