The senator announced he will vacate his seat after just two sitting weeks and before even being able to give his maiden speech, because “he could not in good conscience bring anything less than a 100% dedicated effort to his role”.

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

“I don’t think a person elected to parliament should be anything less than completely dedicated to a role entrusted to them by voters, so I’m resigning to make way for someone who can do that on behalf of the people of NSW.”

He didn’t provide any detail about the nature of his health issues.

One Nation leader Pauline Hanson said she fully supported Stacey’s decision and wished him all the best.

“Warwick Stacey is a man of principle and a great Australian,” she said.

“It is with profound regret that we farewell him from the Senate so soon after he was elected.

“I was delighted when it was announced Senator Stacey had won a seat representing NSW.

“I knew he would bring a wealth of knowledge, experience and expertise to our team along with the strong conservative values that made Australia great.”

Stacey’s election in May’s federal election was a major upset, coming from behind on preferences to edge out Labor for the final seat in NSW after then-Nationals deputy leader Perin Davey lost her spot in the Senate.

“I thank Senator Hanson and One Nation for giving me the opportunity to serve and represent my state in Canberra – it was a memorable campaign that saw our party’s vote rise across the country,” Stacey said.

“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.