"Jacqui and I are not the same, she's Army, and I'm Navy, we do things different, but that's actually a strength, and there are areas of strong common values, particularly around transparency, integrity and accountability," he said.

"We've had plenty of experience working together, we'll be an effective tag team."

Mr Patrick, a former Navy officer, first entered parliament as a replacement for South Australian Nick Xenophon after he resigned for a failed bid in state politics.

Mr Patrick was in federal parliament as a member of the Centre Alliance party, but split from the group in 2020 to serve as an independent.

At the 2022 election, he ran under his own party called the Rex Patrick Team but failed to get re-elected.

While he had been using the years out of politics as government transparency advocate and worked to protect prominent whistleblowers, Mr Patrick said he had unfinished business in Canberra.

"As much as I enjoy my current work as the 'transparency warrior', after careful consideration, I've concluded on balance I could do more for the public good as a senator for South Australia," he said.

"I know the job, I have the skills to hold ministers, bureaucrats and indeed admirals and generals responsible for their actions."

Senator Lambie said her former Senate colleague would be a valuable asset to the Jacqui Lambie Network.

"Rex’s departure from the Senate was a loss for all of us, but particularly South Australia. We need to get Rex back into the Senate so SA once again has a sensible voice representing them in Canberra," she said.

"He works hard to hold the government accountable. He should be in the Senate where he can continue to represent the interests of everyday Australians."

The next election is due to be held by May 2025.

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