Workers at windscreen maker Pilkington in Birmingham have launched a ten-day strike claiming they are being paid £3,000 less a year than employees at a site five miles away.
More than 130 employees at Pilkington Automotive, in Kings Norton, are holding a series of strikes and a continuous overtime ban until July 10.
They claim workers at the Pilkington site in Redditch receive £3,000 a year more in their pay packets.
The firm supplies windscreens to Jaguar Land Rover but the initial impact of the walkout on supplies to the luxury vehicle maker is not known.
Unite regional officer Brian Rickers said: "The crux of the dispute is that a few miles down the road, in Redditch, operators are earning £3,000-a-year more for doing the same job.
"The Kings Norton operatives get paid about £17,000 a year and those at Redditch about £20,000.
"The company has not addressed this issue in the last four years. Our members have said 'enough is enough' with a 78 per cent vote in favour of strike action over a two per cent pay offer which would have further cemented the pay disparity between the two sites.
"The series of strikes, coupled with an overtime ban, could hit the production of windscreens which could then impact on deliveries to car makers Jaguar, Nissan and Vauxhall.
"Given this, we would urge the management to get around the table in a positive fashion and negotiate a fair pay deal and salary harmonisation between the two sites.
"They have not come back to us for any more talks but I am happy to sit down with them."
Non-operative grade staff will stage two, 24-hour stoppages from 6am today and on Monday. The continuous overtime ban for salaried staff started on 26 June.
Pilkington did not respond to requests for a comment.