A construction company manager has been arrested and charged after allegedly threatening to track down a union safety organiser and saying he would "attack you and your family".

Police arrested the site manager at Melbourne-based building firm VCON after a 26-year-old female Trades Hall employee received the disturbing email in her inbox on Wednesday.

Unionists have been campaigning against Melbourne builder VCON/Element Five. Credit:Eddie Jim

"F--k off you scum c--t!," the email began. "If you continue to attack my livelihood I will track you down and attack you and your family!! This is your first and final warning!!"

The site manager was charged with the criminal offence of using a telecommunications service to menace. He has been released on bail.