By Margot Patrick and Max Colchester 

LONDON-- Standard Chartered PLC said Thursday that Chief Executive Peter Sands will step down in June and be replaced by former J.P. Morgan Chase & Co. executive Bill Winters, following a protracted campaign by shareholders and some executives who had grown frustrated with the bank's leadership.

The shake-up was far-reaching: The London-based, Asia-focused lender also said Chairman John Peace will step down in 2016 and that three longtime board members were also resigning. They will be replaced by two new independent directors.

While pressure has been building for months on Messrs. Peace and Sands, the magnitude of the changes surprised analysts and some bank executives. Investors greeted the move, sending Standard Chartered's shares up more than 4%.

The clean out introduces the possibility of dramatic strategic or financial change at the emerging-markets bank. Some analysts said they expect Mr. Winters to take steps to boost the bank's capital buffers by selling new shares, a move that Mr. Sands has long resisted even as investors question the adequacy of the bank's capital levels. Another possibility is accelerating Standard Chartered's retreat from some far-flung locales where the bank lacks much heft.

Mr. Sands, who for months said he wasn't leaving even as the bank's share price tumbled, said it was "the right moment" to hand over the reins to Mr. Winters. "I am delighted that a banker of Bill's caliber will be leading the group through the next phase of development," he said. Mr. Winters, who set up London-based asset-management firm Renshaw Bay after leaving J.P. Morgan in 2009, called Standard Chartered "a special bank." The 53-year-old American was co-CEO of J.P. Morgan's investment bank during a 26-year career at the U.S. lender. He will join Standard Chartered on May 1 and start the CEO job in June.

The announcement marked an abrupt end for one of the U.K.'s longest serving bank chief executives. During his nine-year tenure Mr. Sands guided Standard Chartered up a wave of growth in Asian lending markets. When a slew of British banks needed bailing during the financial crisis the U.K. government turned to Mr. Sands as a key adviser. However in recent years the executive's star has waned. In 2012, the bank was fined by U.S. authorities for violating U.S. sanctions and a year later the emerging markets fueled growth slowed for the first time in a decade.

Despite a rising cost base and a series of profit warnings, the bank initially held back from making drastic changes to its business. The reluctance to change was viewed by some investors as a sign of arrogance born out of past success. Temasek Holdings Pte. Ltd., Standard Chartered's biggest shareholder with an 18% stake, and Aberdeen Asset Management PLC, the second biggest shareholder with a 7% stake, began to agitate for change. Last fall Mr. Peace looked to refresh the bank's succession planning, according to a person familiar with the matter.

In an effort to appease critics, Mr. Sands laid out plans in January to shed thousands of jobs in Standard Chartered's retail bank and shut its stock-trading business, but the plans were regarded by many as insufficient to address the bank's broader problems.

In recent weeks Mr. Sands was privately pressed by some Standard Chartered executives and shareholders to resign, according to people familiar with the matter. At the World Economic Forum in Davos, Switzerland, last month, some clients who met with Standard Chartered executives expressed concerns to them about whether the bank's management was getting distracted, The Wall Street Journal reported. By then the bank had stepped up its search for a successor to Mr. Sands, according to a person familiar with the matter.

The change came quickly. Mr. Winters was approached for the job a few weeks ago, according to a person familiar with the search. The speed of the announcement caught some big shareholders off guard. "It's completely surprised everyone on the upside to get someone of that quality, " said Martin Gilbert, chief executive of Aberdeen Asset Management.

While Mr. Winters in recent years has been a CEO candidate at other U.K. banks, he has little direct experience in Standard Chartered's core emerging markets or in commercial or retail lending. There were a handful of other candidates, some based in Asia, but U.K. regulatory requirements and political scrutiny made it very hard to lure them to a London-based role, people familiar with the matter said.

Mr. Peace dismissed concerns about Mr. Winters's limited Asian experience and stressed that shareholders are supportive of the appointment. Mr. Sands said he would speak with Mr. Winters daily to get him up to speed on the business. Later in the year both men will travel around Asia meeting key clients and stakeholders, he added. Mr. Winters's experience running the European and Asian investment bank at J.P. Morgan and his strong links with the British establishment were a plus, according to a person familiar with the search. He served on the U.K.'s Independent Commission on Banking, a panel of experts which played a key role in reforming Britain's banking sector after the financial crisis.

The changes mark a victory for Temasek, the Singapore state investment company, which had been pressing the bank for years to make changes to its governance and appoint more independent directors. That process was accelerated with the naming Thursday of two new directors: Gay Huey Evans, a former Barclays and Citigroup executive who has also worked for the U.K.'s financial regulator, and Jasmine Whitbread, the chief executive of nonprofit organization Save the Children International, will join the board in April. Longtime directors Ruth Markland, Paul Skinner and Oliver Stocken will step down in the coming months.

More bad news is likely coming for Standard Chartered when it releases its 2014 results Tuesday. They are expected to show a rise in bad loans from customers hit by the commodities selloff.

It is unclear whether much of the old Standard Chartered team will remain in place after Mr. Sands's departure. Mr. Peace declined to comment on how long Mike Rees, Standard Chartered's deputy CEO, plans to work for the bank. Mr. Rees didn't respond to a request for comment.

"I was never going to be here forever," Mr. Sands said Thursday.

Write to Margot Patrick at margot.patrick@wsj.com and Max Colchester at max.colchester@wsj.com

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