Employers at the BMW Oxford plant claim staff have the longest paid breaks within the BMW group.
However, the employees, who assemble 200,000 vehicles a year, are refusing to accept to the new conditions, including the current four per cent basic pay rise.
Under the terms of the new pay deal, management are demanding that the workforce accept an 11-minute reduction in paid leave during their morning and afternoon breaks.
Mini employees currently earn £25,000 a year for a 37-hour week, and currently the plant is one of the most productive in the UK.
An outraged employee said: “If you need to go to the loo during your shift, you have to put up your hand. Sometimes they are relieved by the team leader, sometimes not.
“We have had instances of people having to go in the dustbin,” he added in The Times.
A BMW spokeswoman refuted claims of employees relieving themselves in dustbins.
The spokesperson added: “Employees work on a moving production line, which is stopped during dedicated break times. We have systems in place to ensure that anyone needing to use the bathroom outside of these breaks can do so while another team member fills in for them.”
Unite union officer Roger Maddison said the deal had “more strings to this deal than a puppet show.”
He added: “More and more productivity demands are being made by BMW. Rather than try to claw back every penny it can, BMW should be treating its workforce with dignity.”