NEW YORK -- Simon Johnson would seem to be an unlikely candidate to be throwing stones at the global financial system.

Johnson is the former chief economist at the International Monetary Fund, the organization that uses the economic might of the world's largest nations to rescue smaller countries whose currency is in free fall, all in the name of stability.

He is now a professor at the Massachusetts Institute of Technology's Sloan School of Business and a fellow at the Peterson Institute for International Economics, an economic think tank generally seen as more neutral and non-partisan than most.

But Johnson has become one of the loudest, most articulate voices for the need to break up the United States' largest banks. He argues that they have too much power in both the U.S. and global economies, as well as in the halls of government.

And, Johnson says, that power only encourages them to take far too much risk because of the implicit understanding that the U.S. government would never stand by and let them fail.

The new book he co-authored with James Kwak, "13 Bankers. The Wall Street Takeover and the Next Financial Meltdown," is getting a lot of attention for its argument that the real problem of too-big-to-fail banks isn't the cost of bailing them out, it's the trouble they're bound to cause once they become too big and too powerful.

He says another crisis like the one that sparked the Great Recession is right around the corner, and that in a global economy we're likely to have such crisis every four or five years.

Johnson wants hard caps on bank assets at a fraction of what the major banks hold today. That would force the banks to divide into several much smaller institutions, along the lines of the AT&T breakup into the Baby Bells in the 1980s, although he doesn't specify how a broken-up bank would look.

The most surprising argument in the book is the belief that the U.S. government will eventually move to break up the big banks, despite their power. Johnson argues that while such a radical solution isn't likely to happen in this current round of regulatory reform, it is likely at some point in the next 10 years.

"We're obviously pushing to change policies and we haven't given up hope," he said. "It's tough. We can get out of this. It took Teddy Roosevelt 10 years to change the consensus at the beginning of the 20th century. But from that came the anti-trust movement. People's views have got to shift."

Johnson spoke to CNNMoney.com:

Obviously it's tough to predict future financial meltdowns in advance. But give us a general idea how you think the next crisis in the financial market will develop, what factors will feed it, and what could spark the crisis?

I think the next crisis most likely will come out of emerging markets, kind of like the 1970s. Someone makes a lot of money there, and they park their savings in banks in the U.S. and the U.K. and other parts of Europe that they consider too big to fail. And those banks then go and lend back to the booming parts of the world, which is emerging markets. There's going to be another big debt-fueled boom. People are going to get carried away.

The cycle is not every year or two years, but it's probably more like every four, five or six years. You'll end up where the borrowers can't pay, and the big banks are in trouble. And they're bigger now as a percent of our economy, so it'll be another huge catastrophe.

Do you think there will be the political appetite to save the banks next time, given the anger we've seen this time? If there's political backlash, particularly in this fall's election, do you think that the risk takers on Wall Street will find that the well has run dry the next time they go to that well?

Maybe. I agree there's a lot of populist anger and I think a lot of it is justifiable. What some people call populism we call a sensible understanding of our situation.

But next time, if you face a decision between total global economic collapse and rescuing these banks through unpopular measures, which one are you going to choose? That's the problem and dilemma facing any policy maker unless you change the system.

If you give me that choice next time between massive global collapse, millions plunged into poverty, jobs lost around the world, or rescue these guys, I think I'll go with the rescue. But I'd like us to work now to prevent that choice from being where we are. It doesn't have to be that choice.

So if you had been dropped in to the rooms at the Federal Reserve and on Capitol Hill in September of '08, would you have been making the same calls?

The key thing we have done is we would not been so nice to the banks. The idea that the CEOs get to keep their jobs, the board of directors get to stay in place, everyone keeps their pensions, their bonus, no one is even embarrassed, that's crazy. The Wall Street guys are a pretty cynical bunch. They feel like they did a great trade, and they'll do it again.

You write about how between March 2008 when Bear Stearns went down and September, when the problems with Lehman came to a head, Geithner, Bernanke and Paulson had assumed that the bankers had learned the lessons of Bear Stearns and had unwound from their positions with Lehman. And in fact the lesson they had learned was that "They'll bail Lehman out. We won't get hurt."

The market felt with some justification that Lehman was being given a lot of slack and was going to be allowed to survive. And that's a mistake. Creditors have to be afraid. People have to really fear they're going to lose their money if they lend to these big firms, just like they fear they can lose money if they make unsecured loans to small banks. That's not where we are right now.

But when they get afraid, as they did the day of Lehman's bankruptcy, the economy comes to a screeching halt.

Exactly. We don't want a panic. The point is not to have terror. The point is to have fear.

Who do you bank with? Do you have any banking relationship with any of the 13 banks you identify in your book?

My cash is at a community savings bank in Cambridge (Mass.) and the IMF credit union in Washington. I have an American Express (AXP, Fortune 500) card. They are one of the 13, although I don't think they are as problematic as the others. But I must admit I do have a Citibank (C, Fortune 500) credit card. I keep meaning to get rid of it. My wife has one, too. I have to coordinate us getting joint cards somewhere else. It is an embarrassment.