Questions are being raised over the sale of prime oceanfront land just outside Kalbarri to Sam Barnett, the son of WA Premier Colin Barnett.

Sam Barnett is planning a luxury beachside camping village for the site and intends to charge up to $3,300 a night, making it Australia's most expensive tent accommodation.

Ms Simpkin says Sam Barnett went back on his word. ( ABC News )

But Sandra Simpkin, who sold the land to Sam Barnett, claims the Premier's son originally agreed to buy two parcels of land, known as Lot 51 and 52, for almost $600,000.

She said Sam Barnett told her he wanted the first block cheaper so he could pay $140,000 cash but agreed to pay more for the second, taking the total amount to just under $600,000.

"He said 'I can pay cash for 51 and I'll have to get finance for 52'," she said.

But the sale of the second plot of land fell through, with Sam Barnett telling the Simpkins he could not get finance.

"What he did wasn't illegal, to me it was just unethical the way it turned out," Ms Simpkin said.

"I wouldn't have sold Lot 51 for that price without the combination of the value of both those pieces of land."

Buyer willing to pay more

Another interested buyer, Anne-Marie Bevis and her family, were willing to pay much more for the land but their offer was knocked back because they wanted to pay in instalments.

"To find out that it has gone for that amount, it's definitely worth a lot more than that ... and we were obviously prepared to pay $400,000 for it," Ms Bevis said.

Sam Barnett's resort plans include beach yoga and snorkelling. ( Facebook )

"We didn't tell our friends where it was because even at $400,000 that's cheap, that's cheap for 200 acres on the ocean front."

Last year, Sam Barnett's father — WA Premier and tourism minister Colin Barnett — unveiled a $20 million boost to Mid West tourism including a skywalk in the Kalbarri National Park, just 30 minutes up the road.

It was touted as a major tourism drawcard for the region, promising to significantly increase the number of visitors.

The Premier denies any conflict of interest.

Sam Barnett's company Pearllargo is registered to the Barnett family home and the Premier has declared the land ownership to the parliamentary register of pecuniary interests.

Sam Barnett declined to be interviewed.

His plans for his luxury camping village include horse riding, beach yoga, fishing and snorkelling and he hopes it will open in late September.

The Shire of Northampton said any commercial tourism operation would need council approval and it is yet to receive an application from Sam Barnett.

The shire said the piece of land in question, just outside of the Port Gregory town site, had no access to running water, power or sewerage.