JPMorgan Chase's board Friday "strongly" endorsed Jamie Dimon to continue serving as both chairman and chief executive despite last year's embarrassing $6.2 billion trading loss in the "London Whale" debacle.

JPMorgan had "strong" performance under Dimon "during a time when many other financial institutions with independent chairs experienced great difficulty," the company said in its annual proxy filing with the Securities and Exchange Commission.

The endorsement of Dimon in both roles came as the company battled a shareholder proposal to split the two roles.

The proposal, by the AFSCME Employees Pension Plan and other investors, cited the London Whale losses and pointed to a newspaper article that said the incident "tainted" Dimon's reputation.

"In our view, shareholder value is enhanced by an independent board chair who can provide a balance of power between the CEO and the board, and support strong board leadership," said the proposal.

But the JPMorgan board argued that the company's leadership structure already provides adequate independence.

The board called the company's financial performance strong and said that its response to the "whale" losses, by following through with a thorough investigation, "demonstrate strong, independent oversight."

The endorsement of Dimon came one week after a Senate committee issued a withering report on the London derivative losses that said the bank disregarded its own rules on risk and avoided oversight by the regulator.

On Friday, CNBC reported that the Justice Department has progressed in a criminal probe of London traders involved in the trading losses.

[Photo above of Jamie Dimon via AFP]