Robin Thicke has launched a court battle to protect his hit song Blurred Lines from copyright claims.

The singer and co-writers Pharrell Williams and Clifford Harris Jr are suing Marvin Gaye's estate and Bridgeport Music, the owner of several Funkadelic compositions, after they asserted that the summer smash was not original.

Gayes's family are believed to have complained that Blurred Lines was too similar to the late Motown singer's track, Got to Give It Up while Funakedlic claimed it bared a similarity to their hit Sexy Ways.

In court documents obtained by Hollywood Reporter, the plaintiffs admit that although they were influenced by the former record's classic funk groove, Blurred Lines was original. They say that producing a sound to evoke an era was not copyright infringement.

''Plaintiffs, who have the utmost respect for and admiration of Marvin Gaye, Funkadelic and their musical legacies, reluctantly file this action in the face of multiple adverse claims from alleged successors in interest to those artists.

''Defendants continue to insist that plaintiffs' massively successful composition, Blurred Lines, copies their compositions.''

"There are no similarities between plaintiffs' composition and those the claimants allege they own, other than commonplace musical elements," states the lawsuit. "Plaintiffs created a hit and did it without copying anyone else's composition."

Thicke, Williams and Harris are seeking a declaration that their song does not violate the defendants' rights by copying their songs to avoid paying Gaye's family and Bridgeport a monetary settlement.