Citizens Bank Switches to Arnold.

In an unexpected move, Citizens Bank — New England’s second largest banking firm — has moved its advertising account to Arnold Worldwide from crosstown shop Holland Mark Advertising.

The budget has been in the $15-17 million range, but spending is expe cted to increase to more than $40 million, as Citizens invests more in advertising, direct marketing and interactive efforts, sources said.

“They wanted a global capability,” said Chris Colbert, Holland Mark president, estimating Arnold’s size at about quadruple Holland Mark’s.

An Arnold representative said Citizens desire to increase the scope of its marketing promoted the move. Bank officials did not return calls.

It was unclear whether Holland Mark, which employs about 200, would reduce staffing, C o lbert said. The independent agency shed 20 to 25 employees late last year following the departure of its TJX Cos. assignments.

Arnold, a unit of French firm Havas Advertising, previously worked for FleetBoston, the region’s No. 1 bank, before the accou nt consolidated with Hill, Holliday, Connors, Cosmopulos, Boston. Arnold’s office in McLean, Va., works for PNC Bank, which was not considered to be a conflict with Citizens.

Holland Mark had fashioned ads for Citizens touting the institution as “Not yo ur typical bank.”

Citizens worked with crosstown agency Ingalls for several years before it agreed in 1999 to acquire rival USTrust, then a client of Holland Mark, which in turn purchased Ingalls and retained the Citizens business after the banks united.