WASHINGTON — McKinsey has agreed to pay $18m to settle allegations that it didn’t adequately guard against the risk of insider trading involving investments in companies for which the firm was also a consultant.

McKinsey partners had access to material nonpublic information at companies such as Alpha Natural Resources and SunEdison through the bankruptcy work the consulting firm did for those companies, according to the Securities and Exchange Commission. Meanwhile, another unit of McKinsey, MIO Partners, which managed the partners’ retirement funds, invested in outside hedge funds that were investors in those companies, the SEC said.