The nation’s largest manufacturing trade group slammed the growing influence of proxy advisers on shareholder votes and urged the Securities and Exchange Commission to step up oversight of them, according to a letter reviewed by the Washington Examiner.

The pressure from the National Association of Manufacturers — which counts ExxonMobil, Boeing, Caterpillar, and Microsoft as members — comes as advisory firms Glass Lewis and Institutional Shareholder Services face increasing scrutiny in Washington, D.C.