The West Coast dairy co-op once offered a $10 million Government loan through Shane Jones' Provincial Growth Fund (PGF) appears to have fallen out of favour with New Zealand First.
The party has accused Westland Milk of having a conflict of interest around its sale to a Chinese company.
NZ First MP Mark Patterson said the situation surrounding Westland Milk showed why New Zealand needs a national interest test so "we can counter foreign companies forking out cash to get their way".
He said was "deeply concerned" by conflict of interest allegations made over the sale of Westland Milk Group to Chinese-based Yili Industrial Group.
But just months ago, the Government planned to loan the dairy co-op $9.9 million as part of an "investment in the economy of the whole West Coast".
The loan would help Westland's value-added side of the business.
But that loan offer was withdrawn following news Westland would likely be sold to Yili.
Now, New Zealand First had put the co-op, its sale and its directors in its sights.
Westland's board has accepted Yili's offer of $588 million to purchase the company – the deal now goes to farmers to vote on.
"However, over $1.5 million in bonuses have been offered to top Westland Milk management should farmers vote in favour," Paterson said.
"It is outrageous that chief executive Toni Brendish has been offered $680,000 by Yili if the sale goes through.
"How can we trust that the interests of our farmers are properly represented when top management are lured with big money?"
The sale and retention of key strategic assets need to be taken much more seriously.
"This situation shows the need for a national interest test as part of the overseas investment office process so we can counter foreign companies forking out cash to get their way."
In response to questions about the bonuses, a spokesman said the retention and incentive payment offered to executives was put in place the middle of last year.
"It is important to note this is a normal course of action for such programmes," a spokesman said.
"The chairman will discuss this matter with shareholders at a series of confidential briefings being held this week."