In his maiden speech, LNP senator Gerard Rennick has called for Australia's "unsustainable" immigration levels to be cut and temporary visa numbers reduced.

The son of a farmer said his upbringing had informed his perspective.

"I was taught from a young age about carrying capacity and never to over stock your paddocks. Yet immigration is doing just that, causing major city congestion and overdevelopment on our city fringes."

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On immigration, he praised the federal government for reducing the annual migration cap to 160,000 but urged a reduction in the two million temporary visa holders in Australia.

"The greatest threat to our environment is not carbon dioxide but unsustainable immigration," Senator Rennick said.

"Regional communities are struggling as opportunities, from the lack of infrastructure, go begging."

'International student rules need to be overhauled'

He also called for a radical overhaul of rules around international students, saying universities should foot the bill for their economic impacts.

In a wide-ranging first speech to parliament, the Queenslander signalled he could be a maverick on the government backbench.

Senator Rennick said there was more than 600,000 foreign students studying in Australia who used taxpayer-funded infrastructure.

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"They can work up to 20 hours a week competing with unemployed Australians looking for work," he told the upper house on Tuesday.

"It is time universities and not the taxpayer funded the economic cost of hosting them."

He also wants the universities to underwrite students loans, which totalled $60 billion in 2016.

"Why should the taxpayer underwrite this without a guarantee from universities that their graduates will get a job and repay their debts?"

'Australia's military presence in Middle East must end'

He wants Australia's military interventions in the Middle East including Iraq and Afghanistan to end and described the sale of Darwin's port as "mad".

Senator Rennick, who spent seven years travelling the world, including to Iran and Syria, said the Middle East was the cradle of civilisation.

"The current military intervention in the Middle East has lasted almost as long as World War One, World War Two and Vietnam combined," he said.

"It has gone on for too long and needs to end.

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"Bin Laden is dead, Saddam is dead and there are no weapons of mass destruction in Iraq."

He said Islamic State would only be defeated when the world called out the "Milo Minderbinder" that funds it, a reference to a fictional war profiteer.

It is unclear who Senator Rennick suspects is funding Islamic State.

The controversial sale of the Darwin Port to a Chinese company was an example of foreign investment undermining security, he said.

"Just look at the Darwin Port - neoliberal economics at its finest," the LNP senator said.

"A classic case of ideology gone mad."

'Constitution ineffective'

The Queenslander wants to end concessions for foreign investors and make withholding tax rates made on profits sent offshore the same as those kept in Australia.

Senator Rennick branded the constitution ineffective after 120 years of compromise between state and federal governments.

"It is time for COAG to hold a constitutional convention to clearly define and separate these responsibilities with proposed changes put to a referendum," he said.

He also said the family unit underpinned society, urging the government to preserve the bond between parent and child.

"There is no substitute for mum and dad."

Additional reporting: AAP