Marks & Spencer was one of several retailers launching green strategies this week as part of the 'We're In This Together' campaign.
M&S said it would re-label about 70% of its clothes to encourage customers to wash garments at lower, more eco-friendly temperatures. It said washing at 30degC uses 40% less energy. Shares were down 8p to 713p.
Also supporting the move was Tesco, which aims to sell more eco-friendly light bulbs. Shares rose 4p to 465.75p.
Sainsbury's was giving away its non-plastic "bag for life", although shares were down 4.5p to 530p.
Shares at troubled Blacks Leisure Group fell 12p to 271.75p, not far off its year low, ahead of its full-year interims next week. It warned that profits would come in lower than expected after mild weather hit sales of heavier weight clothing. Glastonbury festival in the summer should help, but is unlikely to solve the group's longer term problems.