Democrats return to Washington this week hoping to rewrite Senate rules on the filibuster. But a closer analysis of congressional action reveals a larger problem: Over the past 22 years, 93 percent of approved measures did not even receive roll call votes.

The frequent use of “unanimous consent” in the Senate is a little-known fact about the upper chamber. It has resulted in a practice of “secret spending” - passing important and expensive bills without debate or even a recorded vote.

But rather than address the unanimous consent rules, a proposal from Sens. Tom Udall, D-N.M., Tom Harkin, D-Iowa, and Jeff Merkley, D-Ore., would eliminate secret holds instead, leaving intact the Senate’s ability to continue secret spending.

According to a memo prepared by the Congressional Research Service, “in the last 10 Congresses [110th-101st], an average of 93 percent of approved measures did not receive roll call votes” and “in the 111th Congress through February 1, 2010, 94 percent of approved measures were approved without a roll call vote.”

Sens. Tom Coburn, R-Okla., and Claire McCaskill, D-Mo., have tried to change that. They introduced a measure last year that prohibited passage of legislation by unanimous consent without first making it publicly available online for at least 72 hours.

Yet when Senate Democrats offer their rules changes this week, the Coburn-McCaskill proposal addressing unanimous consent won’t be one of them.

Unanimous consent is a procedural device used to speed up the legislative process -- as long as no senator objects. In practice, the Senate arrives at unanimous consent not by debate or by thoughtful consideration of bills, but by the Senate “hotline,” an informal telephoned request asking senators to allow measures to be approved by the Senate without debate or amendment.

Senators who object are to notify the majority leader, thereby placing a “hold” on the measure. When senators aren’t in the office to object, they agree to the approval by default. In other words, unanimous consent refers not to the explicit approval of all senators but to a lack of objections.

In some cases, that is as it should be: Many of the measures the Senate passes wouldn’t merit an objection. Simple and concurrent resolutions, for example, are without legal force and don’t even require the president’s signature.

They’re often symbolic gestures. Senators like to commend sports teams for winning national championships, to congratulate counties on momentous anniversaries and to honor the memories of accomplished Americans -- but they don’t like to crowd their calendars to do so.

But occasionally - and most often at the end of a session, when a large proportion of unanimous consent items pass - important and expensive bills also squirm through, sometimes because senators have already headed home and can’t object.

In a span of three days last March, Senate leaders “hotlined” bills that would have cost more than $14 billion. In September, a $600 million border-security bill passed by unanimous consent. And in December, the $1.4 billion Food Safety Modernization Act passed in a flurry of last-minute legislation.

The measure introduced by Coburn and McCaskill would specifically require hotline notifications to be available on a public website for at least 72 hours before a bill or joint resolution could be passed without a vote.

“When a bill is ‘hotlined,’ the public is not informed and neither is the media,” Coburn said in a floor speech last year. “Only the offices of the senators are alerted. It is therefore a form of ‘secret spending.’ Much like a ‘hold’ can be kept from the public, so can the ‘hotlining’ of bills, which can cost billions of dollars.”

Sen. Jim DeMint, R-S.C., angered some of his colleagues last year when he vowed to hold any measures that were not hotlined early enough to allow senators 48 hours to consider them.

Predictably, critics accused DeMint of obstructionism. In the months since, as Democrats have crafted their rules package, they’ve sought to eliminate “secret holds” as part of their larger assault on the filibuster. Yet they haven’t addressed the hotlining process that necessitates holds in the first place.

Coburn put it this way: “There has been much debate over the past year regarding ‘secret holds’ stalling the consideration of presidential appointments or slowing expedited passage of legislation by the Senate. Lost in this discussion has been an issue that should be a far greater concern for taxpayers -- ‘secret spending.’”

Now, more than ever, as Senate Democrats prepare to rewrite the Senate rules, it’s time the issue receives the attention it deserves.

Tina Korbe is a staff writer in the Center for Media and Public Policy, an investigative journalism unit at The Heritage Foundation.