Up to 1,000 vehicles a day are made at Land Rover's Solihull plant
Thousands of workers at car maker Land Rover are staging a 24-hour strike in a dispute over pay.
About 8,000 downed tools at 0600 GMT Monday, for the first time since 1988.
Staff have mounted picket lines outside plants in Solihull, West Midlands, and Gaydon in Warwickshire.
But Land Rover warned action could put the future of the Solihull plant at risk as it would be "increasingly difficult" to justify new investment.
Unions have warned that production will be badly hit by the 24-hour walkout.
The factory normally produces 1,000 vehicles a day, 70% of which are exported.
It added its offer of a 6.5% pay increase over two years was "significantly" above the rate of inflation and industry settlements in the UK.
The Transport and General Workers' Union said its members at Land Rover believed the pay offer should be increased to reflect the contribution they have made to the company's profits.
Workers voted heavily against the offer, arguing that the deal would not give them parity with employees in fellow Ford-owned company Jaguar.
The strike represents an escalation of industrial action, including an overtime ban in recent weeks and the withdrawal from a flexible working agreement earlier this month.
Duncan Simpson, national official at Amicus, said: "It's with reluctance that we've moved to strike action but we hope the company will rethink their position and agree to negotiations.
"We've said we are prepared to meet the company at any time without preconditions.
"The ball is in their court."
Land Rover said its workers enjoyed a comprehensive package of employment benefits that placed them at the top of the car industry pay league.