According to the Community union, which is representing the workers, 109 of the 145 workers in the warehouse are on contracts that were signed before Hong Kong-based investment firm LionRock Capital took over the shoe retailer earlier this year.
Their contracts are more generous than the arrangements in place for newer hires, and the staff are being asked to accept a new deal that will see their pay cut by 15% and holiday allowance reduced by three days, or lose their jobs.
The new employment contracts also offer worse sickness terms, according to the union, and 10-minute breaks and complementary hot drinks will be removed.
Clarks was this week set to begin a 45-day consultation period ahead of the changes.
A Clarks spokesperson said: “Clarks is currently consulting with unions and employees at our Westway Distribution Centre in Street, Somerset on proposed changes to employment terms and conditions for all operatives.
“As we are in a period of consultation, we are unable to comment any further at this time.”
John Paul McHugh, assistant general secretary at Community, told the BBC that it was asking Clarks to “call off the diminishing of terms and conditions”.
He said: “The workers most adversely impacted by these changes are those who have been employees for decades, sticking with the company through thick and thin, stepping up in t