The Ecover campaign, which launches next month, aims to encourage consumers to buy environmentally friendly household cleaning products and Fairtrade clothing by offering customers a £500 voucher for People Tree clothing, and 200 Fairtrade necklaces for runners up.
The on-pack promotion, which lasts for eight weeks, will appear on 500ml bottles of Ecover Delicate liquid, 1.5 litre bottles of non-bio laundry liquid and 1.2kg boxes of formulation non-bio powder.
Clare Allman, marketing manager at Ecover, said: "By choosing pieces from People Tree's clothing collection consumers can wear stylish fashion without having to compromise on ethical standards.
"In turn, by washing their garments with Ecover they can care for these clothes and the environment without having to sacrifice performance. Strategically this partnership will allow us to spread this message to a wider audience."