Spice Girls T-shirts sold to raise money for Comic Relief's "gender justice" campaign were made in a factory where staff earn 35p an hour, an investigation has found.
The charity tops, emblazoned with the message #IWannaBeASpiceGirl, were allegedly made at a factory in Bangladesh where one worker claimed the mainly female workforce were verbally abused and overworked, the Guardian newspaper reported.
The £19.40 garments have been modelled online by celebrities like presenter Holly Willoughby, singer Sam Smith, and Olympian Jessica Ennis-Hill.
Comic Relief has said it is "shocked and concerned" by the report.
The charity said the online retailer commissioned to make the T-Shirts had switched suppliers without telling either it or the Spice Girls, away from an agreed supplier which had been ethically vetted.
A spokeswoman said: "Comic Relief is shocked and concerned by the allegations in The Guardian.
"No one should have to work under the conditions described in the piece."
"To be very clear, both Comic Relief and the Spice Girls carried out ethical sourcing checks on the supplier Represent told us they would be using for production of the T-Shirts."
Online retailer Represent said it was "deeply disturbed" by the allegations, which it described as "appalling and unacceptable".
"Represent has strict ethical sourcing standards for all of our manufacturers," the company said.
"Comic Relief and Spice Girls did everything in their power to ensure ethical sourcing."
Represent said it had chosen a supplier because it believed it had a reputation for upholding ethical standards.
The company said it took "full responsibility" for choosing the supplier, adding: "(We) confirm that this is something that we didn't bring to the attention of Spice Girls or Comic Relief.
"We will make refunds available on request to anyone who bought a shirt."