Bruno Mars is being sued for sharing a picture of himself on Instagram

Earlier this year pop star Bruno Mars shared a picture on social media of himself as a toddler, illustrating his his well-documented love of Elvis Presley, eagerly foregoing 'Throwback Thursday' for what he christened 'Way Back Wednesday'.

It appeared to be a fairly innocuous social media post, but now the Locked Out of Heaven singer is being sued over it by the woman who took the photograph in 1989, when Mars would have been just three or four-years-old.

Catherine McGann is claiming copyright on the shot, which she says Mars used without her permission before posting it to Instagram, Twitter and Facebook, according to documents obtained by TMZ.

McGann is suing Mars and his record label Warner Music for damages and profits earned from the photo, which has garnered more than 1.2 million likes on Instagram alone.

Born Peter Gene Hernandez, Bruno (as his dad first called him) started impersonating Elvis aged four, performing with his family's band The Love Notes alongside his uncle, also an Elvis impersonator.

Being surrounded by a music-loving family fostered in Mars a passion that inspired his entire career, which to date has spanned three studio albums and a string of hits, including Just the Way You Are, Grenade, The Lazy Song and Mark Ronson's Uptown Funk.

Mars has won numerous awards, including five Grammys and in 2016 performed during the Super Bowl halftime show as a guest of Coldplay alongside Beyonce.

He is currently touring the US in support of his 2016 album 24K Magic.