Aviva could axe up to 1,500 jobs as part of its £5.1bn acquisition of its rival Friends for Life, a move which would amount to 4.8 per cent of the combined companies' total work force.
The FTSE 100 insurer said it is unable to provide specifics until the takeover completes, however it will try to keep losses to a minimum.
The two companies head offices, the UK life insurance operations and asset management will be the hardest hit.
"We appreciate that this news may be disconcerting for employees and we would look to ensure that any redundancies are kept to a minimum wherever possible, by using vacancies and natural turnover, for example," it said in a statement.
The shareholders of both companies will vote on the combination on March 26 and - providing they approve - the deal will complete on April 13.