“There is no statute preventing this request, and in light of the precedent of Members of Congress having the opportunity to view highly classified documents, including international agreements during the active negotiations, I trust that you will respond promptly and positively to this request,” wrote Polis in the letter, which is dated February 2, 2016.

Requests for comment from OMB, the Department of Labor and Rep. Polis' office were not returned prior to going to press.

Read: Laws requiring Congress's approval of DOL fiduciary rule move to House

The OMB is in the beginning stages of reviewing the DOL's proposal, a process expected to take anywhere between 60 and 90 days. Congress will then have a two-month period to review the regulation before it is finalized and posted, something proponents of the rule are pushing to happen before the end of President Obama's second term.

Polis, a centrist Democrat, is the ranking member on the House Subcommittee on Health, Employment, Labor and Pensions.

He is one of the more than 100 Democratic lawmakers in both chambers of Congress that have raised some form of concern over the DOL's proposed fiduciary rule.

Recently, he was behind an effort to open another 30-day comment period to review changes the DOL made to the rule subsequent to two previous comment periods and four days of public hearings.

Polis' calls for further transparency of course fell on deaf ears at the DOL, which sent its rule, and whatever revisions were made, to OMB, to this point leaving stakeholders in the dark as to what the changes were made to the proposal.

In his most recent call for transparency, Polis expressed his faith in the DOL's ability to finalize a rule that accommodates stakeholder's primary concern—that the rule, as proposed last year, is fundamentally unworkable.

Read more Benefits Pro coverage on the DOL fiduciary rule

“I am optimistic that DOL has made sufficient changes to the rule that will ensure it succeeds in protecting consumers without disrupting an entire business model, as Sec. Perez has promised on multiple occasions,” wrote Polis, expressing a faith in the DOL and Sec. Perez that he has articulated at various points throughout this debate.

But Polis did say that in his capacity as a subcommittee leader with jurisdiction over the issue, he has a responsibility to “ensure the rule severs the interests of the American People.”

“To fulfill that responsibility, my colleagues and I need the opportunity to see and review the rule as soon as possible with appropriate security,” he wrote.

Polis announced that he has requested permission to review any changes to the proposal during a mark up hearing this week for companion legislation written as an alternative to the DOL's proposal.

He did not vote to advance the legislation, which would require a Congressional vote on the DOL's proposal, arguing that it made no sense to try to kill the rule if it has yet to be seen.

Polis also voted against the Retail Investors Protection Act, which would require the Securities and Exchange Commission to be the lead rule maker in setting a new, uniform fiduciary rule for advisors to IRAs and 401(k) plans.

Polis was first elected to represent Colorado's 2^nd district in 2008, which includes the northwestern suburbs of Denver, plus Boulder and Ft. Collins, Colorado.

Before being elected to Congress, Polis enjoyed considerable success as an entrepreneur. The websites insidegov.com and opensecrets.com estimate his net worth at $388 million.