Unison eastern regional officer Lucas Bertholdi-Saad said the healthcare support workers were “essential to the running of the NHS”, but the trust had used them “to provide care on the cheap”.
“The workers were delighted when the trust finally agreed to give them the respect, recognition and pay they deserved earlier this year,” he said.
“But they had a nightmare before Christmas when they discovered the money in their wage packets was thousands of pounds less than had been promised.
“East Suffolk and North Essex must do the right thing and give staff their due.”
Mr Hulme added: “We have worked in partnership with Unison and all our staff representatives for the past three years to introduce this new, national pay band structure for healthcare assistants.
“We have jointly agreed our approach with Unison and signed a memorandum of understanding. Some colleagues are receiving more than £4,000 in back pay.
“We will continue to work with Unison and talks are ongoing.”