(Adds details on U.S. results in paragraph 5, Chair's quotes in paragraph 4 & 6, shares in paragraph 8)

Nov 7 (Reuters) - Naked Wines slashed its annual revenue and profit forecasts on Tuesday and said CEO Nick Devlin will leave the online wine seller as it bleeds customers in the United States, sending its shares plunging over 20%.

Revenue for the year is expected to fall between 12% and 16% from year-ago levels, while adjusted operating profit is expected to come in between 2 million and 6 million pounds ($2.5-$7.4 million), the London-listed firm said.

The group had previously forecast an 8-12% fall in revenue and profit of between 8 million and 12 million pounds for the full year.

"Current trading in the US has fallen well behind, both in terms of sales and margin," said Founder-Chairman Rowan Gormley, who will take on the role of executive chairman until the appointment of a new CEO.

Naked Wines operates across the US, the UK and Australia, with US accounting for roughly 48% of total revenue. In the first-half, sales in the U.S. fell by 20%.

"My view is that this shortfall is largely to do with execution, which in turn is largely due to Nick Devlin splitting his time across both the role of CEO and US president," Gormley said.

Devlin, who will step down as CEO with immediate effect, will continue as president of Naked Wines USA through the trading season, the company said.

The company's shares were down 20.6% at 35.75p as of 0808 GMT.

($1 = 0.8119 pounds) (Reporting by Prerna Bedi in Bengaluru; Editing by Janane Venkatraman and Saumyadeb Chakrabarty)