A pristine copy of the Mona Lisa, thought to be the oldest ever, has been discovered in Spain.

The copy, discovered by restorers at the Prado Museum in Madrid, is thought to be the earliest replica of the 16th-century original.

According to The Art Newspaper, restorers believe that the work was painted by one of Da Vinci's pupils, working alongside him in the same studio.

The work shows the same woman as the original masterpiece hanging in the Louvre in Paris, but prior to a recent restoration it lacked the landscape background and was covered up.

Representatives of the Prado said they did not realise the significance of the copy prior to the restoration, believing it to have been painted after Da Vinci's original.

The style and composition of the piece then led conservators to suspect that it was painted alongside the masterpiece.

The painting will be displayed in a special exhibition alongside the original in the Louvre in March.

The Mona Lisa is believed to depict Lisa Gherardini, the wife of the Florentine cloth merchant Francesco del Giocondo, sporting an enigmatic facial expression.

Since the varnish on the original has cracked, the subject appears older than her years, while the newly discovered copy gives a glimpse of a more youthful Mona Lisa, as she looked when she sat for the famous painting.