By Sunlen Serfaty and Clare Foran, CNN

(CNN) -- As lawmakers return to Washington after the midterms, a group of former Capitol Hill staffers is calling for the passage of long-stalled sexual harassment legislation before the current session of Congress ends and warning that "time is running out" to enact reform.

In a letter sent to House and Senate leaders, the former staffers write, "we have been encouraged by reports of progress and positive discussion. Unfortunately, time is running out to make these improvements a reality. As the lame duck session begins, many critical and time-sensitive issues will be competing for Congress' attention. We implore you to continue making this one your focus."

Lawmakers are coming back to Washington to a busy few weeks, including an upcoming showdown over spending and funding for President Donald Trump's promise of a US-Mexico border wall that could trigger a partial government shutdown.

But the letter shines a spotlight on the fact that lawmakers have yet to reach a final agreement to overhaul the process for how sexual harassment claims are made and handled on Capitol Hill after the House and Senate passed their own versions of bills addressing the issue earlier this year.

It has been more than a year since the #MeToo movement focused national attention on the issue of sexual harassment and misconduct. Over the past year, Congress has grappled with #MeToo moments of its own as a number of lawmakers on both sides of the aisle were forced to resign after women came forward with misconduct allegations against them.

The letter is addressed to Senate Majority Leader Mitch McConnell, House Speaker Paul Ryan, Senate Minority Leader Chuck Schumer, House Minority Leader Nancy Pelosi and several other lawmakers.

It is signed by Kristin Nicholson and Travis Moore, the co-founders of Congress Too, a group of former congressional staffers who support reforming sexual harassment and discrimination policies in Congress, as well as other former Hill staffers. Some of the former staffers who signed onto the letter have previously spoken publicly about being subject to harassment or discrimination while working on the Hill.

Tuesday marks the one-year anniversary of another letter sent by Nicholson, Moore and more than 1,500 former congressional staffers calling for reform on Capitol Hill to counter harassment.

"Exactly one year ago, many of us joined over 1,500 of our fellow former congressional staff members in urging you to undertake a series of reforms aimed at recognizing and combating the problem of sexual harassment and discrimination on Capitol Hill. Today we write to thank you for your efforts on the issue to date and to express our hope that you will take the necessary steps to bring those efforts to fruition before the end of the 115th Congress," the letter states.

The letter calls on lawmakers to include several components in any final agreement.

"First, it is critical that counseling and mediation be voluntary and that victims have the ability to opt in to these alternatives, rather than being forced to opt out," the letter states.

"Second, it is important that reform legislation provide for meaningful, independent investigation of harassment and discrimination claims," and, "Third, American taxpayers deserve to know when Treasury funds have been used to settle employment claims in Congress."

The signatories of the letter also write that a final deal "should require members of Congress to personally reimburse the Treasury for settlement of any claim of harassment or discrimination committed by that Member."