(CNN) House Democrats are citing flaws in federal policy that have led to unproven and fraudulently marketed coronavirus antibody tests being sold in the United States, according to a memo shared exclusively with CNN.

The memo, by the House Oversight Subcommittee on Economic and Consumer Policy, says that after a briefing last week by federal officials the subcommittee has found the Food and Drug Administration is "unable to validate the accuracy of antibody tests that are already on the market." The committee chairman is suggesting the FDA shut the marketplace down until better procedures are in place.

The FDA has granted emergency use authorization to just seven antibody tests, and there are dozens more awaiting the same authorization. The FDA has also opened a separate process for more than 100 other non-FDA approved tests to be checked for accuracy. As of Wednesday, only 10 tests had completed testing through that voluntary process, according to one federal agency participating. The agency does not know how many total antibody tests have been shipped to health care providers or how reliable those tests are, according to the memo.

The memo states that the FDA told the subcommittee that it had not yet taken any enforcement action against companies with ineffective or mismarketed tests, and that there is no dedicated enforcement staff.

The FDA told CNN, however, that it is carrying out enforcement measures, pointing to a statement by FDA Commissioner Stephen Hahn the day after the briefing.

"We have and will continue to take appropriate action against firms making or distributing unvalidated tests or those making false claims, such as issuing Warning Letters requesting that companies stop their unlawful promotion and detaining and refusing fraudulent test kits at the border," Hahn said.

Rep. Raja Krishnamoorthi, chair of the subcommittee, said the FDA's guidelines have created a "wild west" that will put American consumers at risk.

"What I fear is that they're going to make dangerous life decisions based on those fraudulent testing results," said Krishnamoorthi, an Illinois Democrat.

Regarding the verification process, an FDA spokesperson said, "FDA will continue to consider the risks and benefits of our policies as the emergency evolves and adjust as necessary." The person added: "FDA is constantly evaluating whether our policy needs to change based on new information to protect the public health."

High hopes and challenges for antibody testing

Antibody tests, or serological tests, as they're also known, could play an important role in plans to reopen the economy. Last week, President Donald Trump said such tests will "support our efforts to get Americans back to work by showing us who might have developed the wonderful, beautiful immunity."

But many antibody tests are being developed without FDA approval after the agency relaxed its vetting policy on March 16, saying the move "provided regulatory flexibility [...] in an effort to provide laboratories and health care providers with early access to these tests." The FDA had previously been criticized for being too slow to approve independently developed coronavirus tests, even as the CDC's own early test for the virus proved unreliable.

The problem with antibody tests goes beyond their accuracy: Scientists and health professionals cannot say conclusively whether the presence of antibodies means that someone is immune to Covid-19. They also do not know how long that presumed immunity would last.

"There's an assumption -- a reasonable assumption -- that when you have an antibody that you are protected against reinfection, but that has not been proven for this particular virus," Dr. Anthony Fauci said earlier this week on " Good Morning America ."

Early research has also suggested that not everyone who tests positive for coronavirus will later show a detectable level of antibodies in their blood. "Negative results don't rule out SARS-CoV-2 infection," a senior FDA official said in an interview.

But assuming that antibodies do confer some immunity, it's vital that the tests for them are accurate. Antibody tests can be developed and distributed to the US market in two ways. The first, a more conventional and stringent route, grants companies emergency use authorization after validation of their tests by the FDA. Only seven companies thus far have been approved through this process, though dozens of others have applied.

A second route allows manufacturers to develop and distribute their tests without prior FDA approval. Companies who take this course are asked to self-validate their antibody tests and notify the FDA that they have done so. The only other requirement is to clearly label the product with disclaimers, including noting the test has not been reviewed by the FDA, that neither negative or positive results can be conclusively linked to Covid-19 infection, and that test results should not be used as the only basis for diagnosis. This, too, is being handled on the honor system; the FDA is not requesting testing or marketing materials from manufacturers.

After releasing the tests, the companies have the option to voluntarily have their tests verified through a collaboration that includes the FDA, the CDC, the Department of Health and Human Services, and the National Cancer Institute.

A senior FDA official explained that this second route is an attempt to "strike a delicate balance" between "innovation and making sure that consumers have expedient access to test on the market without delay."

Two studies, out of Stanford and Massachusetts General Hospital , used unapproved antibody tests for research on the community spread of Covid-19, both of which led to valuable insights into the pandemic, the official pointed out.

The CDC did not respond to request for comment by publication time. HHS referred reporters to the FDA. A spokesperson for the National Cancer Institute said that it is "providing performance data of serology testing kits to the FDA" and that it had completed tests for 10 manufacturers and requested kits from another 100, but said that it would defer to the FDA on the results of that verification process.

In his comments on April 18, Hahn acknowledged that some companies have flouted the guidelines, saying that "some test developers have misused the serology test kit notification list to falsely claim their serological tests are FDA approved or authorized."

A recommendation to "clear the market"

Still, members of Congress believe some tests continue to be offered to consumers with promises that may overreach. "Right now there's no authorization required, no validation required, no enforcement by the FDA. And as a consequence, you have a situation where con artists are basically able to succeed," Krishamoorthi said.

Based on the briefing by the FDA, CDC, and HHS, Krishnamoorthi's subcommittee made a list of preliminary findings. They included findings that "companies are ignoring requests from the Department of Health and Human Services (HHS) to voluntarily submit their tests for validation," and that "FDA has failed to police the coronavirus serological antibody test market, has taken no public enforcement action against any company, and has not conveyed any clear policy on serological tests, but rather has issued a series of unclear 'clarifications.'"

As part of their investigation, the subcommittee sent out document requests to at least six companies in the past month that appear to be fraudulently marketing Covid-19 tests. On Thursday they sent another such request to ARCpoint Labs, a South Carolina company operating in 30 states and currently offering antibody testing. The letter to the company claims it appears to be violating FDA policy by offering testing outside of certified labs, as well as overstating the significance of antibody test results and claiming that a positive result for antibodies suggests "'functional immunity' and encourages people to '[d]iscontinue social distancing.'"

"We received Rep. Krishnamoorthi's letter, and we are working diligently to address all of the House Oversight subcommittee's concerns and ensure we are in compliance with current FDA guidelines," ARCpoint Labs CEO John Constantine said in a statement to CNN.

Krishnamoorthi said that he believes the FDA should "clear the market" and start over. "They should enforce their prerogative to prevent the further sale of these tests," he said.

Krishnamoorthi emphasized that antibody testing has "great promise." But, he added, "We don't want to get into this situation where people get sick again because they relied on wrong testing." He said the committee would pressure the administration to make what he called "common sense changes" and continue to seek out companies with ineffective or mismarketed tests.

Above all, the White House needs to be realistic about what we do and don't know about antibody testing at this point, he said. "You can't reopen the economy based on serological testing," he said, "unless you incorporate the science and understand its limitations."

Update: This story has been updated to include the number of additional antibody tests granted Emergency Use Authorization by the FDA after publication.