New Zealand First is accusing banks of putting pressure on Westland Dairy shareholders.
Nearly 94 percent have voted to sell off the under-performing co-op to Chinese dairy giant, to the tune of $588 million.
Primary Industries spokesperson Mark Patterson says farmers he has spoken to have felt they had no choice.
Patterson says they have been told they need to vote for the deal, or sell their shares.
New Zealand First's backing a 'national interest' test as part of the Overseas Investment Office process the Government's considering.
LISTEN TO THE INTERVIEW ABOVE AS PETE MORRISON SPEAKS TO HEATHER DU PLESSIS ALLAN