A girl aged six discovered a desperate note in her Tesco Christmas cards from caged slaves in China forced to work against their will.
Florence Widdicombe, from Tooting, south London, was stunned when she opened the new box of charity cards to send to her friends and found the scrawled message inside.
It is believed to have been written by a foreign prisoner who was made to pack the cards in boxes at a gulag in Shanghai, the Sunday Times reports.
Inside one card, featuring a cute kitten in a Santa hat on the front, it said: “We are foreign prisoners in Shanghai Qingpu prison China.
“Forced to work against our will. Please help us and notify human rights organisation.”
Florence's dad Ben said: “When I looked at the message in the card I thought it was incredible and wondered if it was a prank."
He decided it would be “wrong not to pass it on to its intended recipient. It must have been very risky for those prisoners.”
The note asked the finder to pass it to journalist Peter Humphrey, who was locked up at Qingpu for nine months until June 2015.
He said authorities censored inmates' contact with the outside world so they could not reveal the slave labor.
But another more recent ex-prisoner told him: “They have been packing Christmas cards for Tesco, and also Tesco gift tags, for at least two years.
“The foreign prisoners just package the cards. They pick different designs, put them into boxes, seal them and pack them into shipping cartons.”
The shocking discovery has raised worrying questions over Tesco’s relationship with its Chinese suppliers and their use of forced prison labor.
The supermarket giant's charity cards will this year rake in £300,000 for the British Heart Foundation, Cancer Research UK and Diabetes UK.
Jeremy Lune, chief executive of Cards for Good Causes, said: “Charities exist to help people, not to put them under duress."