Online fast-fashion group Shein is keeping alive a fallback option to list in Hong Kong despite filing for a London listing, the Financial Times reported on Friday, citing people familiar with the situation.

The company confidentially filed papers with Britain's markets regulator in June, two sources told Reuters on Monday, kicking off the process for a potential London listing later this year.

The news has triggered strong opposition from human rights groups in the UK over concerns about Shein's labour practices. Amnesty International UK said the potential London initial public offering would be a "badge of shame" for the LSE.

Shein's plans remain in flux and there is no certainty that it will end up listing in London even if that is the company's current focus, the FT report said.

The company declined to comment on anything related to a potential IPO.

Shein, which was valued at $66 billion in a fundraising round last year, began to explore a listing on the London Stock Exchange early this year, Reuters reported in May, citing sources. Its original plan to list in New York came unstuck following opposition from U.S. lawmakers.

Some senior British lawmakers have also questioned Shein's suitability and called for greater scrutiny of its labour practices, supply chain and use of an import tax exemption.

(Reporting by Urvi Dugar in Bengaluru; Editing by Shailesh Kuber and Devika Syamnath)