Tata Motors on Friday said its global sales increased by 21 per cent in December to 90,294 units on robust demand for commercial vehicles but the sales of luxury brands from Jaguar Land Rover remained flat. Jaguar Land Rover sales were at 21,353 units during December, up just one per cent from last year, Tata Motors said. The sales of Jaguar brand’s sedans were down by 10 per cent last month at 4,332 units.