The senator declared his intention to leave his seat after only two weeks of parliamentary sessions and before delivering his inaugural speech, stating that he “could not in good conscience commit anything less than a fully devoted effort to his duties”.

“Unfortunately, I will be unable to fully dedicate myself to the role as I deal with my personal health issues,” Stacey said.

Stacey’s election in May’s federal contest was a significant surprise, as he surpassed Labor for the last seat in NSW, succeeding after the then-Nationals deputy leader Perin Davey was ousted from her Senate position.

“I express my gratitude to Senator Hanson and One Nation for the chance to serve and advocate for my state in Canberra – it was an unforgettable campaign that saw a rise in our party’s support nationally,” Stacey remarked.

“I thank the people of NSW for trusting me with this role. I thank the staff members who joined my office to work with a brand-new senator.

“I also wish all the best to my successor and the One Nation team.”

Unlike in the House of Representatives, parties are allowed to choose their own replacement for a senator who has resigned.

Hanson said the party would announce Stacey’s successor in the coming weeks.