Homeowners whose properties are being acquired for the NorthConnex road project have accused the NSW Government of low-balling them on prices and then spending up to defend their challenges in the courts.

Key points: Legal team says the Government is hiring top end lawyers to defend its acquisitions

Legal team says the Government is hiring top end lawyers to defend its acquisitions One property owner says he has been offered a third of market value for his land

One property owner says he has been offered a third of market value for his land The Government says it is up to the Valuer General to determine compensation

The Government has been heavily criticised for its approach to acquisitions in the WestConnex project, yet the Baird Government is now accused of taking a similar approach to NorthConnex acquisitions.

Next week, one property owner will invoke a legal defence made famous by the movie The Castle to challenge a decision to acquire his block of land for about a third of its market value.

The ABC can also reveal one business that was originally offered about $500,000 by the NSW Government recently settled action where it was ultimately paid $18 million in compensation.

The Government is acquiring about 50 properties in the Hornsby-Wahroonga area to make way for the $3 billion road project, which will connect the M1 and M2 motorways.

The NorthConnex road project will connect Sydney's M1 and M2 motorways. ( NorthConnex )

Law firm Slater and Gordon is representing a number of affected landowners and said the Government was hiring top-end lawyers to defend the acquisition cases.

Solicitor Lara Nurpuri said many of the offers made to residents were well below market value.

"In our experience the approach has been aggressive," she said.

"The affected landowners are being put in a situation where they're being uprooted from their communities out of sheer force."

Ms Nurpuri said this was reflected in the high volume of cases now before the NSW Land and Environment Court.

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The NSW Roads and Maritime Service (RMS) is listed as defendant in 12 valuation cases across the state in September alone.

"Clients are being faced with a situation where they either take a low ball offer or their only other option is to take it to court," Ms Nurpuri said.

It comes amid news that the bill for the WestConnex acquisitions is set to top $1.5 billion.

"The Government has an allocated budget for property acquisitions so any blow-out of that's got to be taken from somewhere," Ms Nurpuri said.

'They're paying me peanuts'

Construction is underway outside Rocco Fraietta's property. ( ABC News: Kathryn Ward )

One of the properties belonged to Rocco Fraietta.

The 2,900-square-metre block in Wahroonga was recently valued at between $2.5 million and $3 million and Mr Fraietta had planned to subdivide and build a house on the land.

He said the Government had offered him about a third of the market value to acquire the land for the NorthConnex project.

Mr Fraietta plans to challenge the decision in court and said he had already spent hundreds of thousands of dollars in legal fees.

His case begins in the Land and Environment Court next week and Mr Fraietta said he planned to use the so-called "Castle defence" — that the Government must acquire land on just terms.

"They're not paying me a fair market value. Basically they're paying me peanuts," he said.

"At least pay me something that is reasonable. I'm not here to make money but I want something reasonable so at least I can move on with my life."

Mr Fraietta acquired the land himself in 1991 when the state government sold off surplus land from the F3 freeway.

The Government said Mr Fraietta's land value was affected by issues around zoning and flooding.

Land acquisition unfortunate, but unavoidable: Government

The State Government said it was up to the Valuer-General to determine the compensation. If landowners object, they can challenge the valuation in court.

Finance Minister Dominic Perrottet said in a statement that in the past two years, the State Government had put in place more safeguards to protect landholders.

He said the Government was preparing its response to a review of acquisitions that would include improvements to the process to make it "more generous, transparent and compassionate".

"No amount of compensation can completely alleviate the disappointment many people feel when their home is acquired, and as the Premier and Roads Minister have acknowledged, in some cases we could do better," he said.

"Unfortunately land acquisition is a process that we can't avoid if we want to build the long-overdue, congestion-busting infrastructure that the state desperately needs."

Ms Nurpuri said it was not that simple.

"Before it even gets to the Valuer-General stage the acquiring authorities have an opportunity to negotiation with the affected land owner. What we're seeing is that they're rushing through that process," she said.

Ms Nurpuri said low sums paid meant families were being forced to move out of their communities, who were also suffering a huge emotional toll from having to fight through the courts for a fair price.

"They never asked to be acquired," she said.

"If it was up to them I'm sure they would continue living happily in their communities where they've established great relationships, where their kids go to school, they're close to work."

In a statement to the ABC, Roads Minister Duncan Gay said RMS staff had been working hard to minimise the number of people affected by acquisitions.

"I wish we didn't have to acquire a single property," he said.

"There's always room for improvement and I'm pleased the NSW Customer Services Commissioner is reviewing processes on how property acquisitions are managed for major road projects."