Anne Marie Carrie, who today takes over as chief executive of the charity Barnardo's, said children's traumatic experiences had been forgotten in the ongoing political debate over the ethnicity of sex abusers.
Her comments follow high-profile grooming cases involving Asian criminals in Rotherham and Derby which prompted former Home Secretary Jack Straw to accuse some Pakistani men in Britain of seeing white girls as "easy meat".
The UK's child exploitation agency has begun an investigation into the issue, and Ms Carrie warned the Government that its response would probably "remain inadequate" unless it asked a minister to tackle the concerns.
She said urgent action was needed to protect thousands of young girls and boys who are being preyed upon and then abused, raped and exploited for sex.
"Although I thoroughly welcome the recent attention around the issue," Ms Carrie added, "the children at the heart of this crime have been forgotten as discussion has focused on the ethnicity of perpetrators in high-profile cases.
"Barnardo's knows that sexual exploitation is going on in every town and city in the UK and child victims continue to go unidentified as tell-tale signs are overlooked due to a lack of awareness that stretches from front-line children's services to the corridors of Whitehall.
"I have a lifetime of experience working in children's services, but there is nothing more shocking than child sexual exploitation.
"These vulnerable defenceless girls and boys, who crave love and attention, are groomed then abused in the most callous and calculated way, leaving them deeply traumatised and scarred for life."
Barnardo's worked with more than 1,000 sexually exploited girls and boys, including some as young as 10, but it warned that number was "likely to be the tip of the iceberg".
Penny Nicholls, director of children and young people at The Children's Society, said: "Barnardo's findings echo our own experiences in projects run by The Children's Society that help vulnerable children who have been abused.
"Too many children and young people are being sexually exploited in the shadows of society, groomed in secret by heartless gangs of sexual predators or bogus boyfriends who shower vulnerable children with gifts and lure them to be horrifically exploited, sometimes for years on end.
"It can happen to any child and it is time we shone a powerful light on this hidden abuse suffered by children as young as 11 and 12 in cities and towns across the UK.
"We join with Barnardo's in calling on the Government to take urgent action, ensuring a minister has special responsibility for overseeing a countrywide response to combat sexual exploitation."
The Child Exploitation and Online Protection centre will report within six months. Its chief executive Peter Davies said last week that exploitation could not be "simplified along ethnic lines where the victims constitute one ethnicity and offenders another".
A Department for Education spokeswoman said: "This is a complex problem and we are determined to tackle it effectively by working collaboratively right across Government and with national and local agencies."
Danger highlighted by abuse case
Few cases better illustrate the dangers of on-street grooming than Operation Central, an investigation by police, council officers and other agencies into sex abuse in Rotherham.
Five men were given jail sentences totalling more than 32 years after Sheffield Crown Court heard how they abused girls as young as 13 over several months in 2008, having sex with them in a park, in alleyways and in cars around the town.
The victims were in the care of social services and had to be taken out of South Yorkshire when the abuse came to light.
One of them, 13, described how being removed from her family "ripped my heart out" and the abuse had "ruined my one and only body".