US Senator Marco Rubio has written to the UK government, urging it to investigate allegations of “unethical and irresponsible business practices” before allowing ultra-fast-fashion giant Shein to list on the London Stock Exchange.

The letter sent to UK Chancellor Jeremy Hunt and the chief executive of the country’s Financial Conduct Authority underscore the hurdles that still stand between Shein and an IPO.

The company initially filed to go public in New York, but faced significant opposition from politicians, including Rubio, a Florida Republican and China hawk. Though Shein is now headquartered in Singapore, it was founded in China and most of its supply chain remains based in the country.

The company has been dogged by allegations of labour abuses in its supply chain and exploitation of trade loopholes to fuel its growth, both of which Rubio said should be investigated ahead of an IPO.

Both Shein and the UK Treasury declined to comment.

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