Outsourcing giant G4S is to slash more than 1,000 jobs as the company restructures.
It is understood 1,150 jobs are at risk, the majority of which will be cash handlers.
The cuts come as people have used less cash at banks and retailers during lockdown.
Roger Jenkins, GMB National Officer, said: "These cuts are devastating for our members and their families. GMB will fight to the end for every single job.
“They are also another worrying step towards a cashless society - the cash industry really is on a knife edge."
He added: "The collapse of cash industry could have a terrible impact on the elderly and most vulnerable and wreak havoc on small and medium enterprises which rely on cash transactions.
“GMB is calling on the Government to take action to protect the cash industry and all those who will be hit hard is it disappears.”