The 70-year-old retired dairy farmer and his family have accused Hunter Water and the State Government of pressuring them to sell their property to make way for Tillegra Dam.

The Moores' prime 224-hectare dairy property near Dungog is one of the remaining five of 38 properties needed for the 450,000-megalitre dam.

Mr Costa recently rang Mr Moore following a letter from his daughter, Carol Pasenow, who complained the family felt they were being harassed.

Mr Moore said even though the minister confirmed there was no obligation to sell they did discuss how a final sale price for the property would be determined.

"I said if the market falls I'm going to lose money. He said, 'The deal is if you sell, the market value on that day is what you will get.' "

Mr Moore said the conversation concluded with the minister inviting him to call at any time.

"He said if you ever want anything, give me a ring."

Five generations of the Moore family have worked on the property since the 1890s.

"Mum and dad and my grandparents are buried up there," Mr Moore said.

"It's not just that. The land is too good to put under water."

The family is seeking legal advice about how to save their property in the face of looming compulsory acquisition.

Approached for comment this week, a spokesman for the minister said Mr Costa's phone call was not intended to pressure the family.

The minister contacted The Herald last night to further clarify the purpose of his call to Mr Moore.

"The main reason I rang Jim was because I received a message to say that maybe Hunter Water was putting a bit of pressure on them and I just wanted to check that," he said.

Mr Costa said at no stage did he offer advice about how the family should deal with their circumstances.

"I'd really love to be able to help the family out but I can't. I won't make any commercial decisions for them. That's not my job," he said.

"My job is to assist the families through this difficult time and I did say to him that I understand that it's a difficult time for him and his family.

"I certainly didn't feel I gave him the impression now is the best time to sell, because I know for a fact that it doesn't matter when he sells. Why would I say that?"

A Hunter Water spokeswoman said the corporation recognised the sale of land was difficult for the affected families.

"It is very much up to each individual family to decide the appropriate time to proceed with the sale of their property and Hunter Water respects this decision," she said.

All land bought to date had been at market value.