Deputy Prime Minister Barnaby Joyce says he's not thinking about a possible by-election as he waits for the High Court to rule on whether he is eligible to serve as an MP.

'I'll cross that bridge when I get to it, it's a hypothetical but it's an incredible honour to represent the people of New England, it's where I was born,' he said.

'I love New England and I'm going to keep on doing the very best job I can.

Speaking with Sky News, he and his parents are shocked by the revelation that he is a citizen of New Zealand.

'You're shell-shocked. No one thinks that this was going to be the issue,' Mr Joyce said.

'Even now, my parents can't believe it.'

Mr Joyce claims he was first told of his New Zealand citizenship on Thursday last week.

He has since come under criticism for waiting until Monday to publicly declare his dual national status.

'You've got to go away and get a legal opinion...I didn't want to just walk out the front door and say, 'I've heard about this,' because you haven't got your facts right,' Mr Joyce said of the delay.

'I don't pretend to be a constitutional lawyer, so it's time to talk to people who are proficient in that area and get your facts right.'

He says he made the revelation to parliament at the 'first opportunity' when it returned on Monday.

'Like all things, you get your facts right before you start announcing to the world what the issue is and that was it,' he said.

Despite the setback, the Nationals leader said he is 'overwhelmed' by the groundswell of support he has received since the embarrassing situation was made public.

'I'm absolutely overwhelmed by people basically walking into the office, ringing up on the phone and I wish that we didn't have to do this because I want to get back and do the job I'm paid to do,' Mr Joyce said.

'It is what it is.' Under section 44 of the Australian Constitution, anyone who holds dual citizenship is ineligible to sit in parliament.

Mr Joyce's citizenship case will be heard with four others in the High Court in Brisbane on August 24.

The solicitor-general has advised the government that Mr Joyce has a strong case as no application was made on his behalf to become a New Zealand citizen and he was born in Australia.