CEO Maurice Tulloch's decision to avoid splitting Aviva PLC in two has triggered a dispute in the U.K. insurer's boardroom, the Telegraph reported.

The paper said some of Aviva's directors wanted to separate the life and nonlife sides of the business amid fears the company could otherwise become a target for activist investors. Carl Icahn, a noted activist investor, made the headlines in 2015 after trying to force U.S. insurance giant AIG to split into three companies.

"Senior City [of London] sources" told the publication that a split could increase Aviva's stock market value by up to £3 billion and stave off intervention by activist investors. Tulloch has so far opted to continue running Aviva as a composite insurer, combining life and nonlife business.

The CEO disappointed some analysts and investors at Aviva's Nov. 20 capital markets day by failing to announce more dramatic strategic changes. The insurer's share price fell 3.5% that day to close at 405.50 pence a share, and fell further Nov. 21 to 397.70 pence. Aviva's share price has since recovered, and closed at 420.40 pence on Dec. 23.