New Delhi (CNN Business) Slumping sales at Jaguar Land Rover are giving its Indian parent company a huge financial headache.

Tata Motors TTM Shares inplunged as much as 30% in Mumbai on Friday after it reported a loss of $3.8 billion in the quarter ended December — the biggest in Indian corporate history, according to local media.

The loss was entirely due to the plunging value of Britain's biggest carmaker, which accounted for most of Tata's $11 billion revenue in the quarter. Tata took a £3.1 billion ($4 billion) hit as it slashed the value of Jaguar Land Rover on its books to £6 billion ($7.8 billion).

Jaguar Land Rover is under pressure on several fronts. Its sales in China — the world's biggest car market — fell 40% in January compared to the same period last year.

The Chinese auto market has been one of the hardest hit by the country's ongoing trade war with the United States, with car sales in the country falling last year for the first time in two decades.

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