An American film company has filed a lawsuit arguing that the song Happy Birthday to You is public property and should not be subject to copyright.

The song is owned by the music company Warner/Chappell, which collects at least $US2 million per year in licensing fees from films and television shows.

But US company, Good Morning to You Productions (GMTY), which is making a documentary on the tune, alleges it has evidence the song's copyright expired no later than 1921.

It has filed a suit in a federal court in New York City demanding the government invalidate the copyright and force the music company to return what it says are unlawful licensing fees.

According to GMTY, the tune comes from a song called "Good Morning to All," which was composed in 1893 by sisters Mildred and Patty Hill, who sold the rights to Clayton F Summy.

The song in its present form was released in 1924 by Robert Coleman, setting off a series of legal disputes.

"Irrefutable documentary evidence, some dating back to 1893, shows that the copyright to Happy Birthday to You, if there ever was a valid copyright to any part of the song, expired no later than 1921," the lawsuit says.

"If defendant Warner/Chappell owns any rights to Happy Birthday to You, those rights are limited to the extremely narrow right to reproduce and distribute a specific piano arrangement for the song published in 1935."

Mark Rifkin, one of the lawyers representing GMTY, told AFP Warner/Chappell has 30 days from when it receives the complaint to respond, with the option of asking a judge to dismiss the suit for the lack of merit.

A spokesman for Warner/Chappell declined to comment.

AFP