The partnership of equals with Martin Gilbert had been in place since the merger of Standard Life and Aberdeen Asset Management in 2017.

But it had come under growing investor scrutiny as the company struggled, and recently appointed Chairman Douglas Flint said on Wednesday the move to a single CEO would help to simplify reporting lines and the company's strategy.

The tough market backdrop was confirmed in a separate full-year earnings statement in which Standard Life Aberdeen (SLA) said it had seen an increase in net outflows of client cash, mostly from higher margin equities and alternative funds.

Gilbert will continue to serve as vice chairman of the group and chairman of the Aberdeen Standard Investments unit, the company said, and focus on building relationships with key clients and winning new business.

As part of a broader board reshuffle, SLA also said Chief Financial Officer Bill Rattray would step down at the end of May and be replaced by Stephanie Bruce, a partner at consultant PwC.

"The changes that we have announced today have the unanimous backing of the board," Flint said.

"The new structure will strengthen our client focus, simplify reporting lines and facilitate robust execution of the next stages of our transition and transformation programmes."

SLA said net outflows from its funds had increased year-on-year to 40.9 billion pounds ($53.8 billion) from 32.9 billion pounds the year before, more than the 40.3 billion expected by analysts and equivalent to about 7 percent of its assets at the start of the year.

However, it also said a cost-cutting plan begun after the merger was ahead of schedule and it had made a further reduction in expenses of 56 million pounds during the year.

That helped cushion full-year profit from continuing operations, which came in broadly flat at 650 million pounds to beat a company supplied consensus forecast of 13 analysts of 617 million pounds.

Despite the tough market backdrop, the company reiterated its intention to maintain its dividend per share "during the period of transformation", which KBW analysts told clients they took to mean 2020, when the cost-cut plan ends.

SLA shares were up 3.3 percent at 0834 GMT, leading the FTSE 100 index.

(Reporting by Simon Jessop; Editing by Sinead Cruise and Mark Potter)

By Simon Jessop