The 'F' reference links to news of the retail chain last month receiving an F grade in Tearfund's ethical fashion report which ranks retailers and fashion brands on their efforts to prevent child and forced labour, supply chain transparency and worker rights.
Tali Williams, secretary for retail, finance and commerce at First Union, said Farmer's pay rates were an embarrassment for a company that positioned itself on "family values".
"Minimum wages are not enough to live on. Farmers is well behind other major retailers with its pay rates," Williams said.
"What's worse is that Farmers is one of the only major retailers with a performance pay system that actively keeps wages down."
About 80 per cent of Farmers workers were on an hourly rate of less than the prescribed Living Wage of $20.55, Williams said.
Most staff started on minimum wage of $17.70 per hour and Farmers' "unfair" performance review system made it difficult to progress from that, she said.
"The strike action staff are taking, along with wearing T-shirts and stickers that call for liveable wages will raise awareness. Farmers needs to listen to their own family values and return to the bargaining table with a Living Wage for workers."
Farmers chief financial officer, Michael Power, said said the retailer was disappointed that First Union was taking action.
"We are currently arranging mediation (to which the Union has agreed) to assist us in breaking the current impasse," Power said in a statement.
"We have been in bargaining with First Union, which currently represents approximately 25 per cent of our retail staff, since March 2019. We do not agree with what the union has said about Farmers in its media statements."
First Union said the union represents 40 per cent of Farmers' workforce.
Farmers workers have been striking for higher wages and better working conditions since last year with little resolve.
Last year hundreds of Farmers workers across the country undertook industrial action and walked off the job to picket. Strike action ranged from one hour to five hours and affected around 55 stores.
First Union said beauty, sales and service assistants typically found it hard to get a pay increase - not even through its performance review system – which workers had branded as unfair.
"It's disappointing to see Farmers, a company steeped in so much New Zealand history as an iconic Kiwi brand, lagging so far behind New Zealand's when businesses are beginning to acknowledge they need to pay wages that workers can thrive on, not just survive," Williams said.
Farmers is owned by the James Pascoe Group, which also owns and operates jewellery chains Pascoes and Goldmark, along with homeware chain Stevens.
