The retailer has unveiled 80 new commitments under the programme, including the conversion of 50% of its food, home and clothing items across 36,000 lines to Plan A status over the next five years.
To achieve the benchmark, each product must have at least one ethical or sustainable quality, such as being made with free range ingredients.
M&S wants all of its products to comply by 2020 and is encouraging suppliers to put best practice in place.
The company also said it will work with clothing suppliers in Bangladesh, Sri Lanka and India to agree a fair, living wage for workers after a pilot programme in Bangladesh.
Marks & Spencer executive chairman, Sir Stuart Rose, says: “We believe sustainability is a key ingredient of business success and that Plan A will continue to make us more efficient, develop new markets and build customer loyalty. It’s therefore not just the right thing to do morally but also makes strong commercial sense.”
Plan A was launched in 2007 and included 100 commitments in five areas including climate change, sustainable raw materials, waste and health.
The retailer – which says it has achieved 46 of these original commitments up to now – points out that the ethical drive has saved it £50m in efficiencies so far.