"This means the former shareholders become unsecured creditors of a subsidiary of Inner Mongolia Yili Industrial Group...providing what is an interest-free loan to a Chinese state-owned multinational while they are left to struggle financially," Williams said.
His group, which is working under legal advice, is still owed money despite exiting a year ago because Westland's constitution allows it to postpone repaying departing shareholders for up to five years.
"Westland appears determined to adhere to the five year stand-down, despite the likely change in ownership that has been forced by poor management and governance of the co-op."
Westland chairman Pete Morrison, a farmer and significant shareholder, has been approached for comment.
Williams said holding back money from Kiwi farmers when dairying was going through such a difficult financial time was "a disgrace".
The Westland scheme booklet said six company executives would receive total cash bonuses of $1.6m if the Yili sale goes through. The final 25 per cent of the bonuses will be paid six months after the deal is completed.
The farmers in the group going to the OIO are now Fonterra shareholders. They had to buy shares in Fonterra to supply milk.
Yili is offering Westland farmers $3.41 each for their shares. Westland's own independent advisor Grant Samuel has valued them at 88c-$1.30.
Williams said the group members were owed $1.50 a share by Westland - the cost of a share to supply.
The group was not at all concerned about forfeiting the difference between that return and the Yili offer, he said. They knew Westland was looking for significant capital when they chose to leave the company last year and knew they may forfeit a "windfall".
"This is absolutely a principle for us. It's morally wrong for them to still keep our money.
"We want our money in our businesses. The board is using our money to make the deal more attractive to the Chinese.
"Our beef is that they are taking advantage of a technical, legal clause in the old cooperative constitution to continue to hold our money as interest-free loan.
That money needs to go back to New Zealand farming."
Agriculture Minister Damien O'Connor said it was clear the group had a legitimate claim against the company. "They should proceed as they see fit."
He would investigate what the group's claim might mean in OIO consideration of the sale proposal.