A TUC analysis of government figures shows that 83,031 claims were brought in 2015/16, down from 191,541 in 2012/13.
Over the period single claims fell by 69%, while multiple claims fell by 79%.
Unfair dismissal claims fell from 49,036 to 12,652.
Sex discrimination fell from 18,814 to 5,371.
Race discrimination fell from 4,818 to 2,001.
Disability discrimination claims feel from 7,492 to 3,468.