The Heritage Act defines any sites that are 75 years or older, or which contain items that are at least 75 years old, as archaeological sites, even if they are not listed on any heritage registers.
Digging on archeological sites required special permission, which Phillips had not sought, the letter said.
Penalties for breaching the Heritage Act included either 12 months prison time, a fine of $115,000 or both, the letter said.
Heritage Victoria is investigating the alleged breaches and has ordered Phillips to list when and where he found all of the archaeological artefacts in his possession, or face a fine of almost $2000.
