Independent Tasmanian senator Steve Martin has announced he is joining the National Party.

Senator Martin replaced former Tasmanian senator Jacqui Lambie after she resigned over her dual citizenship.

She dumped him from her Jacqui Lambie Network (JLN) party soon after, because he refused to stand aside to allow her to return to Parliament.

Senator Martin was the Mayor of Devonport before he entered federal politics.

"I'm very proud to actually be here today, the first time in 90 years, to be a National in Tasmania," Senator Martin said.

His new party leader, Deputy Prime Minister Michael McCormack, used an interesting analogy in welcoming him to the fold.

"The last National Party member in parliament (from Tasmania) was William McWilliams, a former Country Party leader all the way back in 1927," Mr McCormack said.

"The Tasmanian Tiger was last seen in 1936.

"I sort of liken Steve, a little bit, to the Tasmanian Tiger, in the sense that he's going to be an absolute tiger for regional development, an absolute tiger in there fighting for the interests of Tasmanians."

Ms Lambie was less flattering, arguing Tasmanians had "had a gutful of politics for politicians' self-interest".

"It looks like a marriage of convenience for two increasingly desperate parties — the drifting Nationals in the post-Barnaby era and the country's loneliest Senator, Steve Martin," Ms Lambie said in a statement.

She also claimed the Nationals had a poor track record in Tasmania, having had three attempts at establishing a presence on the island.

"In 2013 they pushed hard for a branch in Tasmania, with registration at state level, but they cut the Tasmanian members loose, abandoned them and even threatened legal action to shut them down.

"What is going to be different this time? Nothing."

Sorry, this video has expired Independent Senator Steve Martin speaks about leaving Jacquie Lambie Network

Defection makes Coalition negotiations slightly easier

Senator Martin said he still had the opportunity to cross the floor and vote against his new party colleagues in the event he did not agree with certain policies.

"If I feel passionate enough about an issue, and I can't convince the party, well the option is that I can cross the floor," he argued.

Labor frontbencher Anthony Albanese said he disagreed with politicians switching parties without first going to an election.

"Senator Martin was elected as a member of the Jacqui Lambie Network, that means he has changed twice since," Mr Albanese said.

"So call me old-fashioned, I think that voters deserve more respect than members of parliament just deciding to change their political allegiances without reference back to those voters."

The addition of Senator Martin to the Coalition means the Federal Government will have to wrangle eight instead of nine crossbench votes in the Upper House, if it wants to pass legislation without Labor's support.

He was already publicly in favour of some Coalition policies, such as cutting company tax.

It is the second defection to the Federal Government ranks in recent months, after former South Australian independent Lucy Gichuhi joined the Liberals.

The High Court ruled Senator Martin was eligible to enter the Upper House, after questions were raised about whether his local government office breached the constitution's ban on public servants being elected to parliament.