Primark has announced plans to improve its sustainability credentials by training 160,000 cotton farmers in India, Pakistan and China in environmentally friendly farming methods by 2022.

The target is part of the retailer’s sustainable cotton programme, launched in 2013, with the aim to use 100% sustainable cotton in all its product categories.

The sustainable cotton is currently being used in women’s pyjamas, a range of denim, towels and bedding, and will be rolled out to menswear and T-shirts next.

The announcement will lead to a five-fold increase in the number of farmers enrolled in the programme, operated in partnership with Cotton Connect, which works to increase commercial opportunities with limited impact to people or the environment, and the Self Employed Women’s Association trade union.

The methods being taught include efficient irrigation, planting in rows with trenches to maximise drainage, and introducing organic pesticides and fertilisers such as cow dung, when possible, to reduce the use of chemical options.

Primark’s ethical trade and environment sustainability director, Katharine Stewart, said the retailer has “taken the view that we’re going to do as much as possible to minimise it [the use of fertilisers and pesticides on crops], but equally what we don’t want is for the farmers not to be able to deal with some of the pests when they have them”.

Stewart said completely organic farming “means a much lower yield”, which would affect the livelihoods of farmers, some of whom in India have increased their incomes by 200% since enrolling on the programme.

Many are calling for a lower yield at a time when the fashion industry faces a sustainability crisis. As one of the most prominent fast-fashion retailers on the high street, Primark is widely seen as a major culprit in unnecessarily encouraging consumers to buy new products.

Stewart said Primark was “one of the few options where [many of its customers] can afford to go and buy clothes” and “a lot of what we sell is what we call fashion basics – T-shirts, jeans, sweater, underwear, socks”, which people get a lot of wear from.

She added that the company was “looking at what we can do to influence customers to wear clothes for longer and also what they can do with them when they no longer want them”. Primark is currently trialling recycling units at its Birmingham flagship where customers can return clothes by the brand as well as other companies.

A spokesperson for Fashion Revolution, which campaigns for holistic change in the fashion industry, said: “We are happy to see Primark stepping up their efforts to source 100% sustainable cotton and, if successful, this should support hundreds of thousands more farmers, especially women, significantly improve their lives and that of their families.

“We would love to see more transparency throughout the whole process, not only on their commitments but on the process and progress along the way. Ideally, they would share the learning, both good and not so good, so that others can learn from it too. We would be hoping to see both qualitative and quantitative reporting and data on the progress and impact of their work.”