The former deputy prime minister also denied he had abandoned his New England electorate after quitting the Nationals to join the Pauline Hanson-led right-wing party.
Mr Joyce said he remained a conservative politician and his move was the most effective way to represent his cause.
"It's not as if I've resigned to go to the Labor party or to the Greens. I'm on the same side of the political fence," he told ABC radio on Tuesday.
"If it's hurt people, I apologise deeply, but if you want to continue on in politics and serve your nation, it was the most efficacious way to do it.
"I'm 58, not 85 and there is more work to do."
The former Nationals leader said his top priority for the remaining two years of his term as a lower-house MP was to serve the people of New England, which he pledged to do "with laser-like focus".
Mr Joyce will sit in the House of Representatives for the rest of the parliamentary term as a One Nation MP before leading the party's Senate ticket for NSW.
But he refused to be drawn on some of Senator Hanson's most controversial public remarks, including comments about banning the burqa after her widely condemned decision to dress up in the religious garment in the Senate.
"I will leave that question to Pauline ... I didn't wear a burqa into the chamber," he said when asked about the stunt on ABC TV on Tuesday.
Mr Joyce was more forthcoming on Monday night, telling the ABC's 7.30 program: "I don't believe that there is a vilification by Pauline Hanson on racial groups".
Senator Hanson hosted the renegade MP for dinner in her office on the night of the burqa stunt.
Deputy Nationals leader Kevin Hogan compared Mr Joyce's defection to that of controversial former federal Labor leader Mark Latham, who later joined One Nation in NSW.
"Barnaby Joyce joins those ranks as having been a previous leader of a party and joining One Nation," he said.
"But I'll leave others to make their judgment about that."
Mr Hogan said there was little that could have been done to deter the defection as Mr Joyce didn't want to continue sitting on the back bench.
Despite polling being at an all-time high for One Nation, it might be inflated as minor-party surges typically softened once an election neared, Australian National University political expert Jill Sheppard said.
Nevertheless, One Nation won a NSW Senate spot in its own right at the May federal election, showing the support was there, Dr Sheppard added.
Voters who might not know most names on the ballot paper would know Mr Joyce and that could prove advantageous, the expert said, noting the former deputy prime minister wouldn't shy away from using his public profile.
"There will be some voters who will follow Barnaby wherever he goes. The coalition will be polling desperately right now to find out how many," Dr Sheppard said.
Recent polls put the share of voters planning to put One Nation first on their ballot papers as high as 18 per cent.
A Resolve poll said 29 per cent of voters would be more likely to support the minor party if it were led by Mr Joyce.
