More Senate staff members stand to be forced out of the health plan for federal workers under a policy adopted Wednesday by Senate Republicans.

The Senate Republican Conference accepted a resolution from Sen. David Vitter (R-La.) to add to the number of Capitol Hill staff already made ineligible for the Federal Employees Health Benefits Program because of the Affordable Care Act.

The resolution makes it the policy of Senate Republicans to make staff members they employ ineligible for the FEHBP “regardless of whether they work in a member’s personal office, committee office, leadership office, the cloakroom or any other office.”

The resolution, which applies only to the Senate GOP, also challenged Democrats to adopt a similar policy.

“Republican senators made a strong, principled statement today in passing my resolution. Washington should have to live under Obamacare just like everybody else until we repeal it,” Vitter said in a statement.

Vitter and some other Republicans have been trying for months to expand what they consider the Obama administration’s overly narrow interpretation of a provision in the ACA. That clause required that once the health insurance exchanges launched in 2014, members of Congress and employees of their “official offices” would become ineligible for the FEHBP, presumably to enroll instead in an ACA plan.

Republicans succeeded in attaching that requirement to the law even though both chambers of Congress were in Democratic control at the time. Interpretation of that provision was one of many controversial aspects of the ACA rollout last fall, in part because the law did not define what positions are part of an “official office.” Nor did it address the employer contribution, which covers about 70 percent of the total cost of FEHBP premiums.

The Office of Personnel Management proposed rules in August 2013 stating that members of Congress should designate the status of their staff positions annually for the following year, that OPM would not question those decisions, and that the employer contribution would continue for those moving to exchange plans. The final version made the employer contribution payable only for those enrolling in a specific ACA option offered in the District and further specified that those forced out of the FEHBP could return to it when they retired, so long as they met standard requirements.

Luke Bolar, Vitter’s communications director, said the intent of the resolution is to apply the law’s provision to employees of committees, leadership offices and other operations directly under the control of a Republican senator or the party—while excluding employees of Capitol Hill’s nonpartisan support operations.

Bolar said that the current policy has been applied unevenly, with some committee employees who work under the control of a chairman or ranking minority member being kept in the FEHBP and others deemed ineligible.

It is difficult to say how many Hill employees had to leave the FEHBP as of this year because “there’s no mechanism that you have to disclose this,” he added. Vitter also has introduced a bill to require such disclosure.

According to an April report from the Brookings Institution, there were 913 Senate committee staff members and 214 leadership staff as of 2009, the most recent year for those figures. Committee jobs are allotted roughly in proportion to the number of senators in each party, meaning Republicans will control slightly above half of them in the upcoming Congress.

The policy “is going to have an impact on morale, recruitment and efficiency” of affected employees, said Bradford Fitch, president and CEO of the Congressional Management Foundation, a nonpartisan group that works with Congress to improve its operations.

“When Congress is not treated like a governmental entity it’s not in the best interests of Congress or the American people,” he said. “These are federal employees and they’re not being treated like federal employees.”

Last fall the potential loss of FEHBP eligibility, particularly to keep it in retirement, was a main concern  among Capitol Hill employees. While the foundation has no data on how many Capitol Hill employees left for other jobs or retired before the end of the year because of it, that did happen in at least some cases, Fitch said.

“They were being kicked around like a political football and didn’t appreciate it,” he said.

However, he added, the foundation also has been told of Hill staffers who are happier with their ACA coverage than they were with the FEHBP, largely because of lower premiums.

The Senate GOP policy likely would not apply until 2016, at least in most cases, under the OPM rules. They specify that eligibility designations must be made by each November for the following year, and that a designation covers the “duration of the year during which the staff member works for the Member of Congress.”

Those forced out of FEHBP are free to get insurance through sources other than the exchanges. That includes family enrollment in the FEHBP as the spouse of someone who is eligible, as are almost all other federal workers.

The annual open season in which federal employees can choose health plans for the upcoming year ended Monday.