'This thing is like an onion," George Costanza once said in an episode of Seinfeld. "The more layers you peel, the more it stinks." Just about anyone who examines the Iran nuclear deal knows how he feels.

Consider the recent bombshell report that revealed that under the terms of a secret agreement it signed with the International Atomic Energy Agency, Iran will be allowed to use its own officials to investigate a military site where it's suspected of conducting nuclear weapons work.

This unprecedented arrangement - which would involve Iranian personnel providing photos, videos, and environmental samples from the Parchin military complex - has stoked concerns that the IAEA investigation of Iran's past work developing nuclear warheads will amount to little more than a public relations exercise.

The IAEA, as well as intelligence agencies from the United States and other countries, has long suspected that Iranian scientists experimented with high-explosive detonators for nuclear warheads at Parchin and conducted additional weapons-related work at other sites.

Despite repeated promises to cooperate fully with the IAEA's investigation, Iran has blocked IAEA inspectors from looking at the Parchin facilities since 2005. It has also razed buildings and stripped away large quantities of earth, further fueling suspicions that Tehran is concealing evidence of past nuclear weapons work.

Why has the IAEA investigation, which began long before the Obama administration's nuclear deal with Iran was signed in July, become a crucial part of the deal? Because the accord stipulates that sanctions can be lifted only after Tehran resolves the IAEA's concerns over the "possible military dimensions" of its nuclear program.

The disturbing news that the IAEA has agreed to outsource some of its responsibilities to Iran has amplified concerns that questions about Iran's past efforts to develop nuclear warheads will be swept under the rug in a rush to lift sanctions.

The IAEA's absurd arrangement with Iran is a far cry from the "anytime, anywhere" inspections the Obama administration promised. The final agreement reached in Vienna allows Iran to delay inspections for up to 24 days, and possibly a lot longer if the U.N. Security Council gets involved in deliberations over possible Iranian efforts to delay inspections.

The disclosure of the IAEA secret agreement has ignited a firestorm in Congress. Many members already resented being kept in the dark on important aspects of the Iran nuclear agreement. Sens. Mark Kirk (R., Ill.) and Marco Rubio (R., Fla.) have called on the administration to release secret letters to foreign governments assuring them that they will not be legally penalized for doing business with the Iranian government.

The IAEA's ludicrous concessions, allowing Iranian personnel to gather possible evidence of past Iranian nuclear weapons experiments, set a dangerous precedent for future nuclear inspections. Letting Iran assume such a prominent role in investigating itself would amount to putting the fox in charge of the chicken coop.

This latest revelation comes atop other controversies over the proposed deal, including:

The temporary nature of restrictions on uranium enrichment, most of which expire after 10 to 15 years;

The failure of the deal to permanently dismantle any important elements of the Iranian nuclear program despite the fact that it dismantles sanctions;

The huge signing bonus Tehran will receive in the form of sanctions relief, which it can use to finance terrorism, a military buildup, or its nuclear ambitions; and

The watered-down inspection arrangements, many of which will sunset after 15 years.

Whether any more unpleasant surprises lurk in other secret side deals is anyone's guess. But it's clear that the administration has oversold the deal.

President Obama promised on the day the deal was finalized that "every pathway to a nuclear weapon is cut off." But after 15 years, Iran will be free to ramp up its uranium enrichment efforts, which will make a sprint to a nuclear breakout much easier.

Moreover, the deal will hold only if Iran complies with its nonproliferation commitments, which it has violated systematically in the past.

The White House appears to be operating according to another George Costanza maxim: "It's not a lie if you believe it."

-James Phillips is the senior research fellow for Middle Eastern affairs at the Allison Center for Foreign and National Security Policy at the Heritage Foundation (www.heritage.org).

-This piece originally appeared in the Philadelphia Inquirer.