Prudential is planning a major cost-cutting drive which could see 1000 jobs transferred to India.
Manufacturing union Amicus announced details of the plan ahead of a Prudential meeting on Tuesday.
Amicus said it was concerned that other financial services companies will follow Prudential's lead and transfer jobs overseas.
According to the Guardian, Prudential plans to move 1000 jobs from its life and pensions centre in Reading to centres in Bombay. The transfers are due to start next year.
Amicus joint general secretary said: "This is a despicable act by the Prudential. Amicus wants to see this decision overturned and we will be looking at all avenues open to us in order to fight this outrageous announcement."
A Prudential spokesman said: "We would want to talk to our staff first before making any announcement of this kind and we would fully expect the union to do the same."
