The package, containing white powder and a threatening note, was discovered by a woman working at the Nenagh office on Friday morning.
It was later declared a hoax.
Speaking to Tipp FM, Minister Alan Kelly said he is used to threats – but he hit out at those responsible for targeting his staff
In his first interview since the incident, Minister Kelly paid tribute to his staff for their resolve and said they were determined to continue with their work
It's not the first time the Portroe native has been targeted since being appointed as Environment Minister.
Last November a caller to the Summerhill office threatened to kill both the minister and his staff while there was also a bomb threat made – earlier this year Minister Kelly said gardaí informed him that dissident republicans had made death threats against his family.
The Minister says that threats and criminal behaviour will not stop him from doing his job.