66% of clothes sold in Primark/Penneys were made from recycled or more sustainably sourced materials over the last 12 months, according to the retailer's third annual Sustainability and Ethics Progress Report.
This marks a 20% increase on the previous year.
Primark trades as Penneys in Ireland.
The company has stores across 17 countries in Europe and the US and employs more that 80,000 workers.
Today's report said the retailer has progressed its commitment to tackle textile waste through the introduction of more clothes that are recyclable at end-of-life.
It said this year it has focused on scaling the volume of its clothes that are circular by design in categories such as denim and jersey and continued to embed its product guidelines on circularity by training colleagues and suppliers.
3% of clothes sold in Penneys/Primark over the past 12 months were circular by design, meaning they met the criteria set out in its Circular Product Standard, including items in the Rita Ora and Disney's The Lion King ranges.
Primark has set an ambition to halve carbon emissions across its value chain by 2030.
Its Scope 1 and 2 emissions reduced by 21% in 2024, compared to 2023, and were 52% lower than the 2019 baseline.
The retailer said the reduction was achieved through energy efficiency measures in its stores and the procurement of renewable and low-carbon electricity.
It reported a 1.9% reduction in total carbon emissions across its value chain since its 2019 baseline year and an 11.6% decrease since last year.
Primark said it expects this reduction to fluctuate in the short-term as the company expands.
The company's report also said that as cotton is the most used fibre in Primark clothing, evolving its Cotton Project - formerly the Primark Sustainable Cotton Programme - and training cotton farmers on more regenerative agricultural practices is an ongoing focus.
It said that about 3,000 farmers have completed a pilot project across India, Bangladesh and Pakistan this year.
They were trained in how to use biological alternatives to chemical pesticides and how to introduce cover crops that protect soil and create new revenue streams.
57% of the cotton clothing sold at Primark contained cotton that was organic, recycled or from the Primark Cotton Project, the report shows.
The company also ran 393 free repair workshops across France, Italy, the Netherlands, UK and Ireland, offering 7,157 places to its customers and workers.
Meanwhile, Primark said it had signed a legally binding agreement with the IndustriALL global union to support collective bargaining for workers in Cambodia's garment and footwear sector.
It is also working with 36 external partners to support workers in its supply chain across 21 programmes, ranging from building financial resilience to protecting against gender-based violence, harassment and mental health issues.
Its worker upskilling programme Sudokkho is now nearly 10 years old and is running in 28 factories in Bangladesh, it added.
Lynne Walker, Director of Primark Cares, said the company's sustainability commitments belong to all of at the company, adding that they were starting to see a real impact.
"The progress we've made in the three years since we launched our Primark Cares strategy has given us the confidence to be proud of the work we are doing. As a brand for everyone, we know we have a huge responsibility to use our scale for good," she said.
"Taking the lead on durability across the industry and proving that more sustainable and longer-lasting clothing doesn’t have to cost more, has been a significant achievement for us," Ms Walker said.
"Continuing to learn as we gather insights and data from across the Primark business and forging meaningful collaboration across the industry will be critical to achieving our 2030 ambitions," she added.
