Jaguar Land Rover CEO David Smith steps down as sales at the two luxury British marques continue to founder.

In a statement, JLR, owned by India’s Tata Motors Ltd., says it would like to “thank David for his efforts in the role and for his service to Jaguar and Land Rover over many years,” but gives no reason for his departure.

Smith, formerly chief financial officer of JLR, has been acting as CEO since the April 20, 2008 death of former CEO Geoff Polites.

Smith will be succeeded by Ravi Kant, vice chairman of Tata, until a permanent successor is announced, the auto maker says.

In 2009, Jaguar’s U.S. sales, its second-largest market, were down 19.4% compared with year-ago to 11,955 units, while Land Rover deliveries fell 11.5% to 26,306, according to Ward’s data.

Globally, Jaguar and Range Rover sales were off 21.0% and 22.0%, respectively.

But with the all-new XJ due for launch in late March and the economy beginning to stabilize, JLR says it expects 2010 sales to “increase significantly.”