By Simon Johnson, co-author of 13 Bankers

Here’s where we stand with regard to democratic discourse on the future our financial system: leading bankers will not come out to debate the issues in the open (despite being approached by reputable intermediaries after our polite challenge was issued) – sending instead their “astro turf” proxies to spread KGB-type disinformation.

Even Larry Summers, who has shifted publicly onto the side the angels (surprising and rather late, but welcome anyway), cannot – for whatever reason – bring himself to recognize the dangers inherent in our unstable and too-big-to-manage banks. Or perhaps he is just generating excuses that will justify not bringing the Brown-Kaufman amendment to the floor of Senate?

So let’s take it up a notch.

I strongly recommend that the responsible congressional committees request and require all assistant secretaries at the US Treasury (and other relevant political appointees over whom they have jurisdiction) to appear before them early next week.

The question will be simple: Please share your calendar of meetings this weekend, and provide us with a complete accounting of people with whom you met and conversed formally and informally.

The finance ministers and central bank governors of the world are in Washington this weekend for the spring meetings of the International Monetary Fund. As is usual, the world’s megabanks are also in town in force, organizing big meetings and small dinners.

Through these meetings dutifully troop US treasury officials, providing in-depth and off-the-record briefings to investors.

Banks such as JP Morgan Chase and the other top tier financial players thus peddle influence, leverage their access, and generally show off. They accumulate information from a host of official contacts and discern which way policymakers – their “good friends” – are leaning.

And what is the megabank whisper mill working on? Ignore the “economic research” papers these banks put out; that is pure pantomime for clients-to-be-duped-later. I’m talking about what they are telling the market – communicated in specific, personal conversations this weekend.

They are telling people that, based on their inside knowledge, Greece and potentially other eurozone countries will default on their debt. Perhaps they are telling the truth and perhaps they are lying. Most likely they are – as always – talking their book.

But the question is not the substance of their whisper campaign this weekend, it is the flow of information. Have they received material non-public information from US government officials? Show me the calendar of the top 10 treasury people involved, and then we can talk about whom to summon from the private sector to testify – under oath – about what they were told or not told.

There is no question that the megabanks derive great power and enormous profit from their web of official contacts. We should reflect carefully on whether such private flows of information between governments and “too big to fail” banks are entirely suitable in today’s unstable financial world.

Large global banks make money, in part, through nontransparent manipulation of information – this is the heart of the SEC charges against Goldman Sachs. But the problem is much broader: the Wall Street-Washington corridor is alive and well on its way to another crisis that will empower, enrich, and embolden insiders (public and private) while impoverishing the rest of us.

The big players on Wall Street are powerful like never before – and they use this power to press for information and favors from sympathetic (or scared) government officials. The big banks also appear hell-bent on abusing that power. One consequence will be further destabilizing global financial markets – watch carefully what happens to Greece, Portugal, Ireland, and Spain at the beginning of next week.

It is time for Congress to step in with a full investigation of the exact flow of information and advice between our major megabanks and key treasury officials. Start by asking tough questions about exactly who exchanged what kind of specific, material, market-moving information with whom this weekend in Washington.