Top executives from some of the world's leading banks will gather for a conference in Frankfurt this week as lenders seek to rebuild trust in the global financial system almost a year after Lehman Brothers collapsed.

But it's going to be a tough sell for the likes of Goldman Sachs, Morgan Stanley and Deutsche Bank.

Even the conference moderator is skeptical about whether the crisis has loosened the banking industry's attachment to a bonus-driven business culture.

Bankers don't seem to have learned a lesson, so regulators will have to do it for them, said Wolfgang Gerke, an honorary professor at the European Business School and the main moderator at the annual 'Banks in Transition' conference.

Bankers are still being rewarded for taking big risks. The basis for measuring a bonus is still short-term profits, particularly on the trading desks at an investment bank.

Regulators are moving to put banks on a shorter leash.

G20 finance ministers and central bankers at the weekend discussed ways to curb some of the excesses that led to a near collapse of the global financial system.

Late on Sunday central bankers decided on a new framework for bank supervision, including new rules on capital requirements, a minimum global standard for liquidity and ways for smoothing banks' vulnerability to economic ups and downs.

HIGH-PROFILE SPEAKERS

Gerke has hosted the 'Banken im Umbruch' conference in Germany's financial capital for the past 14 years. This year's, which comes ahead of a G20 meeting to decide new global finance rules on September 24-25, has attracted an unusual number of high-profile speakers.

Goldman Sachs Chief Executive Lloyd Blankfein is due to speak on Wednesday about banking at the edge of change, while Josef Ackermann, CEO of Deutsche Bank, will talk on Tuesday about the impact the financial crisis had on his bank.

Walid Chammah, co-president at Morgan Stanley, speaks on Tuesday about the outlook for investment banking in the wake of the financial crisis.

Ackermann -- who also chairs the Institute of International Finance, a cross-border banking lobby -- has said banks had made progress with reforms and had not lapsed into old habits.

To say it's business as usual again does not match the facts, he told a conference in Frankfurt last week.

Recalibrated risk models that account for extreme market fluctuations, simpler financial products, reduced leverage and overhauled stress tests are among the lessons learned from the crisis. The bonus culture too had changed, Ackermann said.

Compensation models have been adjusted to align them more closely with sustainable profitability and shareholders' long-term interests, said Ackermann, whose own pay fell by 90 percent last year as bonuses evaporated.

Rebuilding trust will be a tough sell, Gerke said, because bankers now have to deal with not only envy about the size of bank bonuses, but also with public rage at the fact that taxpayers' money was used to uphold the system.

At a meeting in London to set the agenda for the G20 summit in the United States this month, U.S. Treasury Secretary Timothy Geithner said new rules were necessary.

Although regulators and politicians broadly agree that excessive risk-taking by highly paid bankers was one of the main causes of the financial crisis, they struggled to agree how best to structure reforms and a French-led proposal to cap bonuses failed to win broad support.

Public opinion in most European countries...and in the United States as well has been flabbergasted, horrified by the amount of compensation paid to traders and various operators in the financial markets when only eight months ago they were asking for rescue, asking for public money to bail them out, French Finance Minister Christine Lagarde said last week.

Germany Lloyd blankfein Investment Goldman sachs