Brad Pitt and Angelina Jolie are suing over a report that their relationship has hit the rocks.
London-based law firm Schillings said it was launching legal proceedings against the News of the World over "false and intrusive allegations" that the couple had agreed to split.
Reports that the relationship of Hollywood's number one celebrity couple was in trouble began circulating last month and spread rapidly.
On Sunday, Pitt, 46, and Jolie, 34, attended the Super Bowl in Miami with their eight-year-old son Maddox. The couple have ties to New Orleans, the home city of the Saints, who beat the Indianapolis Colts.
Pitt and Jolie bought a French Quarter mansion in the city in 2007, the same year Pitt founded the Make It Right organisation to build houses for low-income residents who lost their homes during Hurricane Katrina.
Meanwhile, 'Tomb Raider' star Jolie visited victims of the Haitian earthquake in neighbouring Dominican Republic yesterday.
Dario Manon, a spokesman for the Dario Contrera Hospital in the capital Santo Domingo, said Jolie toured the hospital yesterday.
He said: "She spoke with several children and a Haitian woman who recognised her and requested help."
The actress was accompanied by Gonzalo Vargas Llosa, a representative of the UN High Commissioner for Refugees and the son of Peruvian writer Mario Vargas Llosa.
Jolie is a goodwill ambassador for the UN refugee agency.
Pitt and Jolie have been partners since they began a friendship while working on the 2005 film 'Mr & Mrs Smith'.
Pitt was previously married to Jennifer Aniston. They divorced in 2005 after five years of marriage.
Jolie was briefly married to Billy Bob Thornton before divorcing in 2003. She was also married to British actor Jonny Lee Miller before they divorced in 1999.
Including Maddox, whom Jolie adopted from Cambodia in 2002, the couple are raising six children: Zahara Marley, Shiloh Nouvel, Pax Thien, Knox Leon and Vivienne Marcheline.