JPMorgan Chase?s regulators will be in the spotlight here on Wednesday, when they testify before Congress on the bank?s multibillion-dollar trading blunder and its implications for the future of Wall Street regulation.

One of the bank?s primary regulators, the Office of the Comptroller of the Currency, will face particular scrutiny for its oversight of the JPMorgan unit responsible for a trading loss of more than $2 billion.

JPMorgan disclosed the loss from its chief investment office last month. Just months earlier, top executives from the chief investment office had travelled to Washington to persuade the comptroller that new trading restrictions threatened the future of the bank. The executives argued that the so-called Volcker Rule could prevent the powerful unit from hedging risk throughout the bank.

?This is important to maintaining the safety and soundness of JPMorgan,? Ina R Drew, then the head of the chief investment office, told comptroller officials, recalled one person who attended the meeting.

Drew was joined by five other JPMorgan executives who echoed her concerns about the Volcker Rule, saying the regulatory crackdown ?could restrict or cast in doubt strategies? that the bank ?successfully employed during the financial crisis?, according to a memo summarising the meeting. The trading blowup that followed has now become a flash point in the fierce debate over the Volcker Rule, which would ban banks from trading with their own money in an effort to prevent them from placing risky wagers while enjoying government backing.

In their testimony before the Senate Banking Committee, regulators are expected to defend their oversight of JPMorgan, which had significant sway with policymakers after emerging from the 2008 financial crisis relatively unscathed. None of the more than 100 regulators embedded in JPMorgan?s Manhattan headquarters kept daily watch over the chief investment office, people briefed on the matter have said, raising questions about gaps in oversight.

In testimony prepared for Wednesday?s hearing, the comptroller of the currency, Thomas J Curry, said that his office ?has been meeting daily with bank management? on its response to the trading loss and its risk management. As part of its review, he said, the comptroller?s office will examine how employees in the chief investment office were paid and whether JPMorgan will try to claw back some of their compensation. He added that the agency was reviewing how to ?improve OCC supervisory approaches.?

The committee will also hear from officials of the Federal Reserve, the Treasury and the Federal Deposit Insurance Corporation. Senator Tim Johnson, the South Dakota Democrat who leads the banking committee, said in a statement that he hoped to hear from regulators ?on potential implications of the loss for supervision and Wall Street reform rule-making going forward?.

The testimony from regulators, while significant, is only the opening act for a hotly anticipated hearing next week with JPMorgan?s chief executive, Jamie Dimon. Once considered Washington?s favourite banker, Dimon is also expected to testify before the House Financial Services Committee.

Federal investigators, meanwhile, are taking a closer look at JPMorgan?s trades. In the wake of announcing that it lost at least $2 billion on positions tied to complex credit derivatives, JPMorgan has received requests for documents and information from an array of federal investigators, including the Commodity Futures Trading Commission and federal prosecutors in Manhattan, according to people briefed on the matter. Federal authorities are examining, among other matters, JPMorgan?s accounting practices and whether the bank?s public disclosures played down the dire state of the trades.

The trades also hit at the heart of the controversy surrounding the Volcker Rule, named after Paul A Volcker, a former chairman of the Federal Reserve. Under the rule, which regulators expect to complete in coming months, banks may still hedge their risk.

A difficult question remains for regulators: What amounts to hedging? JPMorgan officials say the chief investment office initially hedged the bank?s broad exposure to the markets, until the positions morphed into a proprietary bet. But some Democratic lawmakers have seized on the loss to illustrate the case for the Volcker Rule, saying that tough rules are needed to rein in the risk-taking on Wall Street.