Cadbury workers, Teresa Gooch, left, and Donna Bauma, talk outside the Dunedin factory.

Cadbury workers are preparing to fight to keep the Dunedin factory open.

Machine operators Donna Bouma and Teresa Gooch have worked at the Dunedin plant for 16 years.

They are two of 350 workers threatened with the loss of their jobs after Cadbury's owner, American food giant Mondelez International, proposed to close the factory next year.

HAMISH MCNEILLY/FAIRFAX NZ Cadbury factory in Dunedin is to close.

Bouma said staff were "devastated" to be told of the closure by Mondelez management on Thursday morning.

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"It was unbelievable, very surreal … not knowing what's going on."

HAMISH MCNEILLY/STUFF Cadbury workers Teresa Gooch, (left) and Donna Bouma.

Asked whether they were hopeful of keeping their jobs, Bouma replied: "We are going to fight".

"We are going to stay strong, and hopeful."

The chance of the factory not closing "doesn't sound very good", Gooch said.

She took aim at people who were saying they would not buy Cadbury products due to the proposed closure as that action was "going to help put us out of a job".

"It is not the way to deal with it."

Gooch said there was no media gagging by management, and employees were allowed to speak freely.

She said the workers were overwhelmed by the support from Dunedin and New Zealand.

The factory employed a range of people from diverse backgrounds, including single income earners, partners, and whole families.

Mike Kirwood, Et Tu organiser, said union representatives met with management who presented their formal proposal.

The union would respond to Cadbury management on Tuesday.

Staff "weren't happy" about the factory closing, with the Thursday meeting very "sombre", he said.

The Dunedin factory was a "pretty profitable business," but he could not disclose the financials.

Figures from 2015 showed the company reported a profit of $9 million, up from the previous year, on revenue of $291m.

He did not believe the proposal was a "done deal".

He confirmed the union numbers were "virtually 100 per cent".

Kirwood said he was satisfied with the company's response that it had not imposed a gagging clause.

On Thursday, Amanda Banfield, Mondelez vice president for Australia, New Zealand and Japan, said the Dunedin plant was not losing money, "it is not about that".

"It is about its long term sustainability. It is actually more cost effective for us to move this volume elsewhere and that is really the view we have taken."

The company produced crumb chocolate at the site and "Kiwi favourites, such as Pineapple Lumps, and Jaffas, she said.