Alan Williams has suddenly quit as executive chairman of The Bradstock Group following the company's decision to sell off major subsidiaries.
Williams' departure was announced after an extraordinary general meeting in which Bradstock decided to sell its marine and energy reinsurance book to JLT Risk Solutions in a deal worth between £2m and £3m.
New chairman and chief executive Tony Fox said: "The company is too small [for Williams].
"We cannot afford Mr Williams' costs going forward. We had more than 600 people and we now have less than 100.
"We don't have a need for a chairman, a deputy chairman, a chief executive, a finance director and non-executive directors. We can't support that."
The disposal of the marine and energy business follows the sale by Bradstock of its retail arm Insurex Exposure to Alexander Forbes for £12.7m in August.
Together, the two deals have generated a total of more than £15m for The Bradsock Group.
The sale of the marine and energy business is worth an initial £2m, rising to as much as £3m depending on the business's performance in the coming year.
Fox said: "We intend to remain an independent publicy-quoted reinsurance and specialist insurance broker and to create a stable environment for talented entrepreneurs to provide bespoke solutions for a global client base.
"Our short-term strategy is to restructure our current operation to attract new producers and to develop further our core specialist areas."
Fox said The Bradstock Group would invest in new teams and developing global partnerships.
"As a result of our recent disposal programme, we now believe we have the financial resources to achieve our aims," he said.