"James and Sonia are living separately and have been for some time," a representative of the couple told MailOnline. "They are on the best of terms and ask that the family's privacy be respected."
The couple, who have two daughters Peggy, 16, and Mary, 11, reportedly split after James spent two years filming The Hobbit: An Unexpected Journey in New Zealand.
The Irish-born Murphey's Law star met Sonia when he was called back for a final audition to play Hamlet in a theatre production in 1989.
The pair soon began dating although they broke up for a year before reuniting and marrying in 1994.
Despite previous reports that James has had extramarital affairs with his Cold Feet co-star Kimberly Joseph and Irish model Amanda Bunker, no other parties are said to have been involved in James and Sonia's split.
Friends of the couple have said that they simply drifted apart during the years that James was filming the first of Peter Jackson's The Hobbit trilogy in New Zealand.