Royal and Sunalliance (R&SA) staff were shocked last week after human resources director Mandy Perrin resigned after only a year in the job.
An R&SA spokesman said: "Mandy has decided that she wishes to pursue other interests. She goes with our best wishes."
It is understood Perrin left because she was unhappy with the way in which her role and responsibilities were developing. In April this year, R&SA chief executive Andy Haste appointed ex-AXA colleague Paul Whittaker as group HR director.
Her departure coincided with a major management shake-up at board level. Edward Lea and John Maxwell have joined as non-executive directors and John Baker, deputy chairman and chairman of the audit and compliance committee, Nicholas Barber, chairman of the remuneration committee and Carole St Mark are to leave the board at the end of September.