According to an internal memo seen by this publication, Fleming - who was regarded as being a potential CEO - is leaving to “pursue other opportunities.”

In addition to becoming president, Kelleher will take on Fleming's responsibilities overseeing wealth management as well as institutional securities.

Citing someone with knowledge of the matter, the WSJ said Kelleher will move back from London to New York for his new role.

Shelley O’Connor and Andy Saperstein meanwhile have been appointed as the new co-heads of wealth management, reporting to Kelleher.

Shelley has more than 30 years of experience in Morgan Stanley's wealth management business and led the private wealth management business in Southern California before moving to a management role in purchase in 2004. She then headed the private bank before becoming head of field management in 2014.

Saperstein joined Morgan Stanley in 2006 and served as head of field management; then as head of investment products and services before taking up his current role as co-coo of ISG last year.

In other changes, Jim Rosenthal, in addition to his role as COO, will now lead the development of Morgan Stanley's digital offering for financial advisors and wealth management clients.

"Digital technology and its potential for our business is one of the most important strategic opportunities we face," the memo said.

Lastly, Jeff Brodsky, in his continued role as head of human resources, will now report to Gorman, reflecting his increased focus on talent and development, it added.