Blake Lively allegedly threatened to leak embarrassing private texts from Taylor Swift unless the pop star agreed to back the actress publicly in her feud with co-star Justin Baldoni.
The revelation appears in a legal letter filed on Wednesday by Baldoni's lawyers in response to Ms Lively's request to stop their subpoena to the singer.
The court filing also alleges that Ms Lively, 37, urged Ms Swift, 35, to delete the text messages between them.
It is the latest twist on the collapse of the pair's once-close friendship.
In the letter to the judge obtained by the Mail, the legal team of Baldoni, 41, led by Bryan Freedman, maintained that the order aims to obtain information 'relating to witness tampering and evidence spoliation' - specifically that Ms Lively had attempted to 'coerce' the singer into publicly siding with her.
Baldoni's attorneys received information that 'Ms Lively requested that Taylor Swift delete their text messages' - which, according to insiders, may have contained details about relationships and private confidences.
It also claims Ms Lively's lawyer Michael Gottlieb had contacted Ms Swift's attorney and demanded 'that Ms Swift release a statement of support for Ms Lively, intimating that if Ms Swift refused to do so, private text messages of a personal nature in Ms Lively's possession would be released'.
Ms Swift's representatives purportedly addressed the 'inappropriate and apparently extortionate threats in at least one written communication' sent to Mr Gottlieb, according to Mr Freedman.
'It is those communications that [Baldoni's legal team] seek to obtain by way of subpoena, as they would evidence an attempt to intimidate and coerce a percipient witness in this litigation,' the document states.
In December last year, Ms Lively filed a legal complaint against Baldoni, accusing him of sexual harassment and starting a smear campaign against her. Baldoni strongly denies that and has sued her in response.
Ms Swift has reportedly been trying to distance herself from the scandal and her friendship with Ms Lively.
