A Sydney couple, whose battle to rebuild their home uncovered a major corruption scandal within the NSW Government's Mine Subsidence Board (MSB), say they have not been able to return home for almost five years.

Key points: Frank and Louisa Kozak's fight to get back into their house led to a major corruption scandal

Frank and Louisa Kozak's fight to get back into their house led to a major corruption scandal Damage from mine subsidence has left the couple out of their home for 5 years

Damage from mine subsidence has left the couple out of their home for 5 years They say their rebuilt home is in need of repairs

Frank and Louisa Kozak went to the Independent Commission Against Corruption (ICAC) after complaining to the government for years about dodgy practices at the board, which administers a multi-million dollar fund to repair homes damaged by underground coal mining.

Since then, the ICAC has heard allegations a district manager at the MSB took at least $300,000 in kickbacks from building contractors he employed to fix hundreds of damaged houses.

The couple live in an area affected by mine subsidence near Picton, south-west of Sydney.

They first noticed defects in their home in 2006 and sought compensation from the MSB.

"There were cracks in the walls, you could put your hand through the cracks, water was gushing behind the walls, floors were uneven," Mr Kozak said.

"At first they said it wasn't mine subsidence but eventually they agreed that the house was a write-off and it needed to be demolished and rebuilt."

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In 2010, the Kozaks were relocated to another house nearby while the work was done.

"They told us it would probably take 12 months and then we could move back in," Mr Kozak said.

"We've been in this house for four-and-a-half years. This will be our fifth Christmas in this house."

Engineers found ground movement had caused damage to the Kozak's home. ( Supplied )

For years, the Kozaks complained to the MSB and various government ministers about poor workmanship, misconduct and conflicts of interest.

Frustrated by what they perceived to be a lack of government action, the Kozaks turned to ICAC.

What its investigators uncovered was explosive.

"We approached ICAC and gave them the information," Mr Kozak said.

"They got back to us and said, 'yes, we've found something but it's under investigation'.

"We were told not to say anything. It took about 15 months and then a hearing was opened up and it all came out."

The Kozaks say they were told the work on their house would take about a year. ( Supplied )

At hearings in April, the ICAC was told the former district manager of the MSB's Picton office, Darren Bullock, took at least $300,000 in kickbacks from two builders over seven years.

It is alleged Mr Bullock took cash payments from the builders, in exchange for awarding them the contracts to repair homes.

Mr Bullock allegedly spent the money on house extensions, a swimming pool, cars and family holidays.

Mr Bullock denies the allegations.

Mr Bullock (left) denies allegations he took kickbacks from builders. ( AAP: Dan Himbrechts )

The Kozaks said they felt vindicated by the ICAC investigation.

"It was a big weight off our shoulders, but I don't understand why we're still here," Ms Kozak said.

"They promised us a new home. I haven't got that. There are cracks in the concrete and damage from water leakage. It's all repairable but they just won't do it," Mr Kozak said.

They believe corruption could be far more widespread across NSW — a possibility the ICAC is examining.

ICAC commissioner Megan Latham is expected to hand down her findings next year.

NSW Finance Minister Dominic Perrottet issued this statement to the ABC: