Managers at the National Institute of Agricultural Botany, which took over East Malling Research in 2016, have been unwilling to engage with Prospect and Unite union over the annual pay award.
The company also refused to supply basic financial information to the unions.
The unions rejected a pay offer of 1%, with an additional 0.4, 0.6 and 1.2 % for good, very good and exceptional appraisal marks.
Prospect negotiator Claire Dent said: “This is a below-inflation pay rise – effectively a pay cut for more than 85% of staff at NIAB EMR.
“We are also deeply unhappy that the company refused to take any of our suggestions on board and imposed this pay award part-way through the negotiations.
“The company has also failed to explain why the pay envelope has been set so low or why it was unwilling to provide a full picture of its finances.”
Prospect is calling on management to reopen negotiations and look at other measures to compensate staff and make them feel valued.
In the meantime, the union is balloting members on the offer.
NIAB has also sent paperwork to staff about promotion and bonuses without consulting union representatives.
At a recent meeting, members agreed that the new arrangements were not fit for purpose and expressed concern that staff representatives were not being consulted on processes that are key to staff career progression.