Activist shareholder Voce Capital Management LLC is once again criticizing Argo Group International Holdings Ltd. after the insurer received a subpoena from the SEC.

The disclosure of an investigation by federal regulators "vividly illustrates the need for immediate and sweeping changes" at the company, Voce Capital said in a press release. Argo on Oct. 8 announced that its independent directors are conducting a review of the company's governance and compensation matters, following the board's approval of compensation-related changes in August and a subpoena the company received from the SEC for documents connected to its disclosure of certain compensation-related perquisites.

Voce Capital, which owns about 5.4% of Argo's shares, earlier this year nominated five independent directors to the company's board. It later withdrew those nominees.

The activist investor requested a meeting with Argo's independent directors in August and made several proposals, including the retirement of several company board members and the creation of a special committee. Those proposals were rejected.

Voce Capital said it is still open to working with Argo's board on the matter, but said it would not hesitate to "hold [the board] accountable through whatever process we deem to be in the best interests" of shareholders if the board continues to refuse recommended changes.