People’s United, a Bridgeport, Conn.-based bank with a significant presence in Massachusetts and northern New England, has announced that John P. (Jack) Barnes will immediately take over as CEO and president.

Barnes had stepped in to fill the position on an interim basis after the April departure of his predecessor Philip R. Sherringham, who left abruptly by "mutual agreement" with the bank’s board.  The board soon after indicated that Sherringham had not been moving quickly enough to act on the bank’s strategy of growth by acquisition.

People’s United, with $23 billion in assets, announced that Barnes was elected unanimously after a three-month internal and external search for Sherringham’s replacement.

"In the three months that Jack has led People’s United as interim President and CEO, he has clearly demonstrated his strong leadership skills and the ability to execute on our strategy of delivering growth and increasing shareholder value," said George P. Carter, chairman of the board, said in a statement.

Barnes is a relative newcomer to the bank, having joined as a senior executive vice president and chief administrative officer following the bank’s acquisition of Chittenden Corp., where he was an executive, in 2008. In his position at People’s United, Barnes managed information technology, operations, real estate and business services for the bank.

The announcement comes shortly after Mark Fitzgibbon, an analyst with Sandler O’Neill & Partners in New York, predicted in an investors’ note that Barnes would be elected CEO in late July or early August.

People’s United has had a busy year. It quickly purchased the failed Lowell-based Butler Bank after Butler was seized by the FDIC in April, it has officially begun the process of changing the names of its subsidiary banks in New England despite legal opposition from similarly named competing banks, and last week it announced it would purchase two new banks and establish a presence in downtown Boston.