Beyonce is under fire for reportedly using sweatshops for her Blue Ivy clothing line

Beyoncé's line of gym wear is made by Sri Lankan workers earning as little as £4.30 ($6.20) a day, according to a report by the Sun on Sunday.

The Sun reported that a 22-year-old seamstress said she earned £87 a month for a near-10-hour shift, five days a week.

The clothing range, known as Ivy Park, is a joint venture between Beyonce and Topshop. The Sun reports that it Topshop claims it "empowers women through sport."

Leggings go for around £40 - roughly 10 days wages for their producers - and tops sell for between £20 and £40.

A spokesperson for Arcadia Group, Topshop's parent company, declined to immediately comment.

A spokesperson for Ivy Park told Women's Wear Daily: "Ivy Park has a rigorous ethical trading program. We are proud of our sustained efforts in terms of factory inspections and audits, and our teams worldwide work very closely with our suppliers and their factories to ensure compliance."

The Women's Wear Daily piece points out that the minimum wage in Sri Lanka is 400 rupees, or $2.68, so while the workers making Blue Ivy clothes are low paid, they in fact make over double the minimum wage.

Labour Shadow Chancellor Jon McDonnell joined protesters outside Topshop in London on Sunday in support of two cleaners who had been "victimised" for joining a union.

It's been a bad few weeks for Topshop owner Sir Philip Green. He has traded blows with Labour MP Frank Field in a row over the collapse of 88-year-old retailer BHS and been called the "unacceptable face of capitalism" by Tory MP Richard Fuller.

Green, who bought BHS in 2000 for £200 million but sold it for just £1 last year, has called for one of the key MPs probing the collapse to "stand down from the inquiry immediately as he is clearly prejudiced."

Field, the Labour MP and chair of the Work and Pensions Select Committee, recommend stripping Green of his knighthood if the billionaire for failing to meet the pension deficit left by the failing chain.

The Work and Pensions Select Committee is holding a joint inquiry into the collapse of BHS alongside Parliament's Business Select Committee.