The alleged sexual assault dates back to the 1980s and is said to have taken place in the London area.
Merseyside police first received the report on Wednesday morning, before referring the case to Scotland Yard.
The allegation will now be assessed by officers from Child Abuse and Sexual Offences Command.
The UK investigation comes after the New York police re-opened a 2004 case against the 65-year-old.
An allegation was made by former aspiring actress Lucia Evans, published in the New Yorker, that Weinstein forced her to perform a sex act on him in his Miramax offices in 2004.
NYPD detectives are also reviewing public allegations against Weinstein to identify, locate and interview any possible victims or witnesses.
A flood of sexual harassment, assault and rape claims have surfaced against the producer since The New York Times published a report alleging a history of abusive behaviour dating back decades.
A police recording published in the New Yorker also seems to show Weinstein admitting to groping Italian model Ambra Battilana Gutierrez .
The Hollywood producer has previously denied any allegations of non-consensual sex.
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