As Congress works on an eleventh-hour plan to end the standoff over the shuttered government and potential default on the federal debt, regulators are laboring to oversee business activities with a skeleton crew.

Even after the federal budgets are restored, regulators such as the Securities and Exchange Commission, the Food and Drug Administration, and the Occupational Safety and Health Administration could take weeks to return to full operations. Meanwhile, new drugs are going unapproved, workplace discrimination claims are going uninvestigated and companies are getting a temporary break from new SEC rules.