(Reuters) -Online fashion firm Shein is preparing to file a prospectus with Britain's Financial Conduct Authority for approval ahead of a potential London float which could value it around 50 billion pounds ($63.70 billion), Sky News reported on Sunday.

The confidential filing could take place as soon as the coming week, the report added, citing sources.

Chinese-founded Shein did not immediately respond to a Reuters request for comment.

Shein, valued at $66 billion in a fundraising last year, started engaging with the London-based teams of its financial and legal advisors to explore a listing on the London Stock Exchange early this year, sources told Reuters in May.

The fast-fashion company stepped up preparations for its London listing after its attempt to float itself in New York faced regulatory hurdles and pushback from U.S. lawmakers.

However, senior British lawmakers are also questioning Shein's suitability for a London listing and calling for greater scrutiny of the business. Shein, in response, has said it is strengthening governance and compliance.

($1 = 0.7850 pounds)

(Reporting by Akanksha Khushi in Bengaluru; Editing by Ros Russell)