The Rehab singer is furious Georgette Civil sold one of the love letters she penned to then-husband Blake Fielder-Civil while he was in prison.

Winehouse has launched legal action for copyright infringement and is asking for the five-figure sum as compensation.

A source said: "Amy was furious the private letter was used to make money."

No date has yet been set for the hearing.

Winehouse has always had a fraught relationship with Civil, who previously accused the singer of turning her son to drugs.

The Back to Black star married Blake in May 2007 but they began divorce proceedings in July. Their marriage will officially be over when the proceedings are finalised on Friday.

WINNING HIM BACK

However, Amy is currently trying to win back her former love and has been sending Blake a series of Internet messages posing as her cat and recently begged him to take her back during an emotional phone call.

Her insistence on pursuing a reunion has sparked a family feud with her mother Janis Winehouse, who has threatened to cut off contact with her daughter if the pair reconcile.

Janis and Amy's father, Mitch, blame Blake for Amy's descent into drug addiction.