Melbourne man Adam Storch, 38, is wanted for failing to report to police as a registered sex offender and has not made contact with authorities since his release from prison on July 12.

Convicted for sex offences against both children and adults, he has been sighted twice in the eastern suburb of Kilsyth.

He was last seen in the CBD on July 12 at a business on Swanston Street between 12.10pm and 12.45pm with another man, who police have asked to come forward.

He is described as "highly mobile" and known to visit Preston, Reservoir, Heidelberg, St Kilda, Prahran, South Melbourne and CBD.

Assistant Commissioner Neil Paterson urged the public not to approach Mr Storch but instead report sightings to triple zero.

"We know that when sex offenders don't comply with their obligations, they are more like to commit offences," Mr Paterson said.

"Victoria Police have undertaken extensive enquiries, detectives have undertaken extensive enquiries, and have not been able to locate him."

An investigation into his family, friends, past associates and banking and phone records has failed to locate him.

Mr Paterson said Mr Storch was known to use many aliases including "Dominic Gatto" and was mostly likely travelling on public transport.

Mr Storch is free to live in the community but must provide authorities with a current address, which he has failed to do.

"If Mr Storch is watching this media tonight, we urge him to attend the closest police station," he said.

Two images of Mr Storch have been released because he had put on "a significant amount of weight" while in prison, police said.

He has "Vanessa" tattooed on his neck.

Anyone who sights Mr Storch is urged to contact triple zero or Crime Stoppers on 1800 333 000.