Comic Relief has said it is “shocked and concerned” by a report alleging that Spice Girls T-shirts sold to support its “gender justice” campaign were made by staff paid the equivalent of 35p per hour.

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 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.”

The spokeswoman added that the retailer, who could not immediately be reached for comment, had “taken full responsibility” for the alleged matter and would be refunding customers.