Online fast fashion firm Shein is planning to file paperwork for a potential London share listing as soon as this week, according to reports.

An initial public offering (IPO) could value the company at around $66bn (£51.7bn).

The firm, which was founded in China and now headquartered in Singapore, stepped up preparations for a share sale in the UK after it faced regulatory hurdles and intense scrutiny in the US.

A Shein spokesperson declined to comment.

Shein has in the past been linked to unethical business practices, including forced labour allegations.

A confidential filing with the UK’s Financial Conduct Authority could lay the groundwork for a major London stock market share sale.

While the move may come this week, Sky News, which first reported the story, said it could be moved to later in June.

Shein filed paperwork for a potential New York listing with the Securities and Exchange Commission (SEC), the Reuters news agency reported in January.

However, the company has faced pushback from US lawmakers over concerns about its links to China as tensions between Washington and Beijing intensify.

Last year, a group of US lawmakers called for Shein to be investigated over claims that Uyghur forced labour is used to make some of the clothes it sells.

“We have zero tolerance for forced labour,” Shein told the BBC at the time.

The company has also faced scrutiny outside the US as speculation grows that it may list its shares in London.

Last month, a reported suggest that workers for some of Shein’s suppliers are still working 75 hours a week, despite the company promising to improve conditions, a report suggests.

A new investigation by Swiss advocacy group Public Eye followed up on its 2021 report, which found a number of staff across six sites in the Chinese manufacturing hub of Guangzhou were doing excessive overtime.

According to the group, who interviewed 13 employees from six factories in China supplying Shein for its latest investigation, excessive overtime was still common for many workers.

Shein told the BBC it was “working hard” to address the matters raised by the Public Eye report and had made “significant progress on enhancing conditions”.

Shein has grown rapidly since it was founded in 2008, and was one of many online businesses to boom during the Covid pandemic lockdowns.

Its formula of offering a wide range of cheap clothes – backed up with campaigns on Instagram, TikTok and other social media – has turned it into one of the biggest fashion retailers in the world.

It relies on thousands of third-party suppliers, as well as contract manufacturers, near its headquarters in Guangzhou, and is able to turn around a new item in a matter of weeks, rather than months.