Easter trading laws are back on Parliament's agenda and a union representing retail workers says it has a fight on its hands.

The union representing sawmill workers is seeking government intervention after an Upper Hutt mill announced it will close with the loss of up to 40 jobs.

The National Distribution Union (NDU) and Finsec have joined forces to create FIRST Union, which organisers say will represent 28,000 workers.

The NDU's 23,000 members are in retail, transport, textiles and wood while Finsec represents 5000 finance sector workers.