Boys and girls as young as 10 are being sold for just €6,600 by black market gangs operating in the Punjab in India, an investigation by The Sun has claimed.
They are preying on the children of Nepalese refugees and destitute Indian families, according to the newspaper.
British home secretary Theresa May said child trafficking is a “truly abhorrent crime” and urged the UK’s National Crime Agency to investigate the findings.
She told the newspaper: “No child, anywhere in the world, should be taken away from their home and forced to work in slavery.
“That is why we introduced the landmark Modern Slavery Act last year, which included enhanced protections for potential child victims of slavery and sentences up to life imprisonment for those found guilty.
“We encourage The Sun to share its disturbing findings with the Police and National Crime Agency so that appropriate action can be taken against the vile criminals who profit from this trade.”
The Sun reported that the desperate children are being sold to wealthy British families to be used as unpaid domestic servants.
According to the newspaper, a trader named Makkhan Singh lined up youngsters for an undercover reporter to pick from and said: “We have supplied lads who have gone on to the UK.
"Most of the ones who are taken to England are Nepalese.
“For the supply of a boy, minimum 500,000 rupees [around €6,600]. Then you will have other costs associated with taking him to the UK, but that’s your responsibility extra to what you pay us.
“Take a Nepalese to England. They are good people. They are good at doing all the housework and they’re very good cooks. No-one is going to come after you.”
A 7.8 magnitude earthquake struck Nepal on April 25 last year, killing almost 9,000 people and leaving millions in need of aid.
It is estimated that millions of people across the world are victims of modern day slavery, trafficked across borders and forced to work in servitude.
In October 2015 the Modern Slavery Act was brought in to crack down on modern day slavery and protect victims of trafficking.