The company has not officially confirmed how many posts will be lost, but Sarah Carpenter of the union Unite said she believes around 280 people will be made redundant.
Furthermore, the company's headquarters office in Manchester is to close, with some other jobs transferring to smaller premises elsewhere in the city.
Ms Carpenter said the closure of the main office would be a "heavy blow to staff".
Overall, Friends Provident is thought to have around 465 staff in Manchester.
"Unite is angered that there has been a total failure by Friends Provident to involve staff representatives in this review, despite being the recognized union," Ms Carptenter commented.
She added that the union will be consulting with employees, as well as seeking an "urgent meeting" with management to discuss the planned redundancies.
Established in 1832, Friends Provident offers pension and insurance services to both retail and business clients.