A 45-day consultation period with staff began on Thursday and the Trust – which currently has about 9,500 employees – said it was working with the Prospect union “to minimise compulsory redundancies”.
Prospect said though cost pressures were partly to blame, “management decisions” also contributed to the Trust’s financial woes.
The union’s deputy general secretary, Steve Thomas, said “once again it is our member who will have to pay the price”.
“Our members are custodians of the country’s cultural, historic and natural heritage – cuts of this scale risk losing institutional knowledge and skills which are vital to that mission,” he said.
The Trust is running a voluntary redundancy scheme, and is expecting that to significantly reduce compulsory redundancies, a spokeswoman said.
The job cuts will affect all staff from management down, and everyone whose job is at risk will be offered a suitable alternative where available, the spokeswoman added.
Following consultations, which will finish in mid-to-late August, the cuts will be made in the autumn.