Workers at the McVitie's plant in Glasgow are staging a demonstration in a bid to avert the factory's closure.
The owners have set out plans to shut the site next year, with the loss of almost 500 jobs, and shift production to their other plants in the rest of the UK.
The biscuit maker has operated at Tollcross in the east end of the city for almost a century.
Unions have called for action by the UK and Scottish governments to save it.
McVitie's owner Pladis said the Tollcross plant would close in the second half of 2022 to address "excess capacity" at its plants, and move production to other factories in the UK.
On Saturday morning, workers and their families gathered to stage a demonstration against the plans.
GMB Scotland Secretary Gary Smith said generations of locals had worked there, and that the company had thrived recently - despite the pandemic.
He said the workers wanted to "protect food manufacturing in their community, they want investment in their plant and jobs for the next generation".
"In Tollcross, workers and their families will send a loud and clear message to Pladis: 'This is our factory, it's our future, and we are going to fight for it'," he said.
There have been concerns raised about the future of the plant, which produces Hobnobs and Rich Tea biscuits among other products, for a number of years.
Pladis said its plans to shut the historic site were subject to a consultation process with its 468 employees.
A spokesman said: "We understand the news of this proposal has been difficult for our colleagues at Tollcross.
"Our priority is to provide them with the support they need while we carry out a full and meaningful consultation process."
A Scottish government spokesman said the situation was a "key priority for the government", and that an action group would convene in the coming days with a view to securing a sustainable future for the site.
But he added that this required "meaningful engagement from Pladis and we would encourage the company to work together with us".
The spokesman added: "Along with Scottish Enterprise, Glasgow City Council, Clyde Gateway and the Trades Unions, we will work constructively with the company to see what support can be provided in order to change this proposed decision.
"The action group will carefully consider all alternative options which come forward during this consultation process, including those from the trades unions, at Tollcross."