A newsletter from the union, sent to staff members at Friends Life, highlighted issues such as a lack of employee engagement, less flexible working conditions and poor pay terms.
It said: “Friends Life does seem to be making money due to the pain employees are going through and so can share some money with them as well as the shareholders.”
The comments come as Friends Life reported pre-tax profits of £178m in its half-year results up to 30 June 2012. This was down from £406m in June 2011.
The February newsletter said negotiations about pay claims were progressing, however, its pay survey showed that staff felt they were working harder than ever but were not being rewarded. The survey also noted that employee benefits had been eroded.
Meanwhile, negotiations over 150 jobs that have been put at risk since December are continuing at Friends Life.
A spokesman for Friends Life said the firm took employee engagement seriously and has recently introduced new flexible benefits, adding: “We have had considerable change within the company in the past year and we understand this has been challenging for our colleagues, as it has been in many businesses and sectors over recent years.”
The insurer is separately in talks about the future of the Sesame Bankhall Group, which it owns.
Denis Mitchell, managing director of Cornwall-based Demelza Lifestyle Financial Planners, said: “A lot of insurance companies need to make changes. We have had issues with getting adviser charging in place.
“Friends Life is a combination of a lot of businesses. We have used it for protection and had the odd administrative issue. This may be due to all the different brands.”