Pop singer Justin Timberlake is suing the News of the World for libel, saying its report that he cheated on his girlfriend, Cameron Diaz, is untrue.
Timberlake has consistently denied suggestions of a split with Diaz
Media lawyers Schillings issued libel proceedings after a request for damages and a retraction of story was refused.
Managing partner Simon Smith told BBC News Online the company would be pursuing the claim with "some vigour".
But a spokeswoman for the Sunday newspaper told BBC News Online it would be standing by its story.
"We will vigorously defend these proceedings in court," she added.
Timberlake has consistently denied suggestions of a split with 31-year-old Charlie's Angels actress Diaz.
The former 'N Sync singer, who won two Grammy Awards this year, has previously been linked to Janet Jackson and the actress Alyssa Milano.
But for many he will be forever associated with Britney Spears, from whom he broke up in 2002 amid reports of heartbreak and acrimony.
"I was addicted to Britney," he confessed later. "But that's love for you.
"No one knows what went on between us except us," he added. "What I will say is I was never unfaithful."