Tesco has suspended production at a factory in China following allegations forced prison labour was used to pack charity Christmas cards.
It comes after the Sunday Times reported a six-year-old girl from south London found a message from Shanghai prisoners hidden in a box of cards.
“Please help us and notify human rights organisation,” the message said.
Tesco said it was “shocked” by the report, adding: “We would never allow prison labour in our supply chain.”
The supermarket said it would de-list the supplier of the cards, Zheijiang Yunguang Printing, if it was found to have used prison labour.
According to the Sunday Times, Florence Widdicombe opened a £1.50 box of Tesco cards to find that one of them – featuring a kitten with a Santa hat – had already been written in.
In block capitals, 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.”
A Tesco spokeswoman said: “We were shocked by these allegations and immediately halted production at the factory where these cards are produced and launched an investigation.”
The supermarket said it has a “comprehensive auditing system” to ensure suppliers are not exploiting forced labour.
The factory in question was checked only last month and no evidence of it breaking the ban on prison labour was found, it said.
Sales of charity Christmas cards at the company’s supermarkets raise £300,000 a year for the British Heart Foundation, Cancer Research UK and Diabetes UK.
The retailer has not received any other complaints from customers about messages inside Christmas cards.
The message in the card urged the recipient to contact Peter Humphrey, a journalist who was formerly imprisoned at Qingpu on what he described as “bogus charges that were never heard in court”.
After the Widdicombe family sent him a message via Linkedin, Mr Humphrey said he then contacted ex-prisoners who confirmed inmates had been forced into mundane assembly and packaging tasks.
Mr Humphrey – the author of the Sunday Times story – also said that censorship in the prison had increased, cutting off his usual methods of contacting prisoners he had met before his release in 2015.
“They resorted to the Qingpu equivalent of a message in a bottle, scribbled on a Tesco Christmas card,” he said.
It is not the first time that prisoners in China have reportedly smuggled out messages in products they have been forced to make for Western markets.
In 2012, Julie Keith from Portland, Oregon, discovered an account of torture and persecution by a prisoner who said he was forced to manufacture the Halloween decorations she had purchased.