(Reuters) -Diageo Plc, the world's biggest spirits company, on Monday said CEO-designate Debra Crew will assume the top role on an interim basis immediately as outgoing boss Ivan Menezes undergoes medical treatment.

Long-time boss Menezes, who was set to retire at the end of this month, is currently in hospital receiving treatment for medical conditions including a stomach ulcer, the company said in a statement.

"Over the weekend, we learned that Ivan's recovery suffered a significant setback due to complications, which followed emergency surgery on the ulcer," Diageo said.

Diageo, the maker of Johnnie Walker whisky, Tanqueray gin and Don Julio tequila, in March had appointed Crew, 52, to replace Menezes, with her becoming one of only a handful of women to lead a company in Britain's blue-chip FTSE 100 index.

(Reporting by Eva Mathews in Bengaluru; Editing by Sherry Jacob-Phillips)