SMILE! Alleged diamond thief captured clear as day on CCTV

The man pictured above is wanted over an alleged jewellery theft last month.

Police said a man attended the Collins Street store about 12.30pm on March 16 after making an appointment to purchase a diamond.

While looking at the diamond, it is alleged the man swapped it with a fake.

Investigators have released images of the man who is described as being aged in his 30s with a medium build and a bald head.

He was wearing glasses, black jumper, blue jeans, black runners and was carrying a black backpack.

Anyone with any information about the theft is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au