Westenberger will leave on May 16, when the firm will also publish its half-year results, Brewin Dolphin said in a statement.

The company said its board has already started a search for a permanent replacement for Westenberger, who had been finance director at Brewin Dolphin for five years.

Brewin Dolphin's business "continues to perform in line with expectations, with continuing growth in income and profitability," the firm said.

KBW analysts said in a note they viewed the departure as a "negative event" for the shares, due to "how quickly this change has come about, and the minimal time period for handover". They reiterated their "market perform" rating on the stock.

Active managers such as Brewin Dolphin are facing competition and fee pressure from index-tracking passive funds, leading to a round of consolidation in the sector.

Brewin Dolphin reported a 15 percent rise in full-year first-quarter profit to 57.6 million pounds ($80.20 million) in November.

Its assets under management rose 3.5 percent in the quarter to end-December, to 41.5 billion pounds, it said in January.

(Reporting by Carolyn Cohn; Editing by Alexander Smith)