Wax-jacket maker Barbour, the upmarket brand beloved by City types, could be faced with four weeks of industrial action as it enters into the New Year.
Employees at the company's warehouse in Gateshead, Newcastle will walkout over plans to introduce new shift patterns.
The strike, which is scheduled to start on 5 January, comes after more than 130 employees stopped work over the same issue before Christmas.
Fazia Hussain-Brown, Unite's regional officer, said:
Barbour's sign or be sacked ultimatum is bullying and anti-family.
Many of the workers struggling to get by on less than the living wage are the sole breadwinner and have family or caring responsibilities.
Earlier Barbour said the changes were needed to meet customer demand and employees would receive "substantial" pay rises.
In recent years Barbour jackets have transitioned from posh to cool after being worn by fashionable celebrities like Lily Allen and Alexa Chung.