Executive search firm DHR International said only three FTSE 100 companies have a deputy CEO, half as many as two years ago.
Frank Smeekes, of DHR International, said: "Shareholders do not want businesses to go through any period of uncertain management or strategic drift.
"This can act as a drag on a company's share price as well as impact on profits.
"Having a deputy CEO, who is already known to shareholders and has board experience, prevents this and can provide continuity if the board decide to search for an external candidate and then wait for them to finish their notice period."
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