And critics say the low wages and long hours at the Mauritian factories amount to exploitation.

The shirts have been worn by Ed Miliband, Nick Clegg and Harriet Harman, all keen to display their feminist credentials – even though the Deputy Prime Minister last night admitted he had ‘no idea’ where the garments were made.

But The Mail on Sunday has toured a factory producing the T-shirts, where workers earn just 6,000 rupees a month – equivalent to £120.

The figure is just a quarter of the country’s average monthly wage, and around half of what a waiter earns. Each ‘feminist’ T-shirt costs just £9 to make, but high street chain Whistles sells them for £45 each – a figure it would take the women a week and a half to earn.