* Q3 sales down 0.7 pct
* Emerging markets remain challenging
* Shares down 2.9 pct (Adds analyst, executive departure, shares)
LONDON, April 16 (Reuters) - Diageo, the world's largest spirits maker, reported slower quarterly trading on Thursday, hurt by tough comparisons in Britain and retailers reducing inventory in Southeast Asia.
The maker of Johnnie Walker whisky, Smirnoff vodka and Guinness beer said net sales in the three months to March 31, the third quarter of its financial year, fell 0.7 percent, against some analysts' expectations for a sales increase.
Even after stripping out a specific hit from changes in timing of shipments in Latin America and the Caribbean, sales would have been well below expectations, RBC Capital Markets analyst James Edwardes Jones said.
"We believe consensus expectations of 1.5 percent (sales growth) for the full year look too optimistic," he added.
Diageo shares were down 2.9 percent at 1911 pence by 0837 GMT.
The quarterly report is the last of its kind for Diageo, which will conduct only half-year reporting from its next financial year.
Compared with the previous six months, sales trends worsened in Europe, Asia Pacific, Latin America and the Caribbean, but improved in Africa and North America. Analysts were hoping for signs of improvement in the United States, Diageo's largest profit driver, especially after positive industry data from research firm Nielsen.
"Our performance in the quarter reflects continued tough conditions in the emerging markets and subdued consumer demand in some developed markets," Chief Executive Officer Ivan Menezes said in a statement.
The company blamed its weaker performance on British sales that fell by a high single-digit percentage.
Diageo cited a tough comparison with the same period last year, in which sales were boosted as customers stepped up purchases ahead of an expected increase in alcohol duties.
It also said that this year's sales were weakened by regulatory changes in Indonesia, which would ban beer in some markets, and retailers keeping less inventory in Southeast Asia.
Diageo announced separately that the president of its Africa business, Andy Fennell, will leave the company at the end of its financial year and be replaced by John O'Keeffe, managing director of Guinness Nigeria. (Reporting by Martinne Geller; Editing by Mark Potter and David Goodman)