The main union at Jaguar Land Rover’s British plants has raised concerns over the company’s plans to assemble vehicles in China and Saudi Arabia.

Unite, the UK’s biggest union, is demanding an urgent meeting with senior executives from JLR’s Indian owner, Tata, to seek assurances over the future of five British plants.

The call follows the announcement this week JLR chief executive Ralf Speth had signed a letter of intent paving the way for an automotive partnership in Saudi Arabia.

JLR also assembles the Land Rover Freelander in India. Unite general secretary, Len McCluskey said:"I have personally asked for an urgent meeting with Tata's chairman and vice-chairman where I expect assurances over the future of Jaguar Land Rover's UK plants.

"Three years ago Unite was delighted to back Tata's acquisition of Jaguar Land Rover against fierce opposition. At that time we received assurances that the quintessentially British branded products would always be designed, manufactured and built in Britain. We also received guarantees that the future of Halewood, Castle Bromwich, Solihull and the two design studios would be secure for the long term.”

JLY said its UK plants are running close to capacity. The Halewood Freelander and Evoque factory is already working three shifts, seven days a week, to keep up with demand.

Discussions between JLR and the Saudi government are at a preliminary stage, although opportunities have already been identified in aluminium component production.

The world's largest integrated aluminium complex, a joint venture between Saudi Arabian Mining Company and Alcoa of the US, is due to begin production in 2014 at the Ras Al Khair facility - creating potential opportunities for the automotive sector.

JLR has pioneered aluminium body development in the premium car segment, using lightweight metals for the XJ and the new Range Rover, the first luxury sports utility vehicle with an all-aluminium monocoque body structure.

The company’s expansion plans follow a sharp rise in JLR sales to emerging markets, contributing to a 32% increase in global retail sales to 324,184 vehicles in the 11 months to November 30. In the current calendar year, sales in the Middle East and North Africa have increased by more than 9% to 11,418 units.

Earlier this week Speth said: "We are committed to further international partnerships to meet record demand for our highly sought after vehicles. The kingdom of Saudi Arabia is an attractive potential development option, complementing our existing advanced facilities in Britain and recent manufacturing plans to expand in other countries including India and China. "

He added that if the Saudi development goes ahead it will “complement our existing expansion in the UK and elsewhere".