Britain's Musicians' Union is calling on performers to come clean and tell audiences if they lip synch rather than sing live.

The union is urging promoters, producers and artists to back its campaign for lip-synching to be clearly labeled during TV shows, in pop arenas and on stage. The union suggested that a lip-synching logo could be flashed up on television or on posters and tickets for shows.

The union's president says that the union was in no way opposed to the use of technology, especially in smaller theatres where the producers could not afford to pay for a full orchestra.

The issue hit the headlines when British pop veteran Elton John took a swipe at Madonna, saying she cheated her fans by miming on stage. Collecting a song-writing award in 2004, he suddenly launched into a tirade against Madonna when he discovered she had been nominated for Best Live Act. Madonna swiftly denied lip-synching and pointedly said she did not spend her time trashing other artists.

The union campaign was launched on BBC Television's "The Culture Show" with a poll showing that 71 percent of those questioned backed its stance.