Customers of some of the UK’s biggest fast-food chains including Pizza Hut and Burger King may be eating meat that comes from chickens reared in poor conditions, claims a new report from a leading animal charity.

Amid growing concerns about the intensive and large-scale production of meat – with some birds growing so fast that they routinely suffer from lameness and skin lesions – World Animal Protection (WAP) has ranked eight of the leading brands according to their commitment, ambition and transparency to improve chicken welfare globally.

In the UK it has been calling on Nando’s to urgently improve its chicken welfare policies, but the results of its analysis, published on Wednesday, reveal the chain has for the second consecutive year received a “poor” rating.

The most improved is KFC, which has leaped from “poor” last year to “making progress”. In July it became the first UK fast food chain to sign up to the European Chicken Commitment – new welfare standards for farmed chickens that will improve the welfare of millions of birds in the UK, Ireland, Belgium, Germany, Netherlands and Sweden.

For its report the charity analysed the policies of leading chains with retail operations in the UK; Burger King, Domino’s Pizza Group plc (covering Europe), KFC, McDonald’s, Nando’s, Pizza Hut, Starbucks and Subway. It also included Domino’s Pizza Inc which operates in the US and Canada.

Burger King, Pizza Hut and Domino’s were all classed as having a “very poor” approach to managing chicken welfare. Only three of the chains assessed were classed as “getting started” or “making progress” on improving chicken welfare standards – KFC, Starbucks and Subway. Most companies are still failing to take chicken welfare seriously, the report said.

Ian Woodhurst, WAP UK farming campaigns manager, said: “While it’s encouraging to see companies like KFC starting to take chicken welfare seriously, many people in the UK are expecting to see other companies, such as Nando’s, also do the right thing for chickens. These companies face a real reputational risk if they don’t take action now to move away from the use of fast-growing chickens that suffer from catastrophic health issues and live their short lives in unnecessary pain.

“Consumers are becoming increasingly concerned about animal welfare and these iconic companies have the power to put an end to this suffering that they are causing for the sake of their own profits. We will continue to speak up for chickens and consumers to put pressure on companies to make real change.”

In the UK sales of red meat have fallen in recent years, but chicken – seen as a “healthy” meat – has seen sales rise. Fast-food chains are also increasingly launching “vegan-friendly”, plant-based versions of traditional meat patties.

The charity is calling on the chains to take a lead on animal welfare and ensure that any chickens being served at their restaurants are reared in humane conditions.

Nina Arnott, a spokesperson for Domino’s plc, said: “Domino’s Pizza Group is committed to ensuring high standards of animal welfare throughout our supply chain. We have strict welfare policies and regular checks to ensure our supply partners are 100% compliant. All our chickens are reared with natural daylight and enrichment, including perches and bales of straw. We do not have any battery cages in our supply chain. Domino’s has published a number of targets for 2020 to ensure we continue improving our welfare standards.”

A spokesperson for Subway said: “Subway takes animal welfare seriously by working closely with our suppliers to ensure that animals are treated well in accordance with Subway’s global animal welfare policy. All UK and Ireland chicken suppliers and their producers must, as a minimum, comply with EU animal welfare legislation and globally we support the principles of the Farm Animal Welfare Council Five Freedoms, which is a framework to safeguard and continually improve animal welfare.

A spokesperson for Burger King said: “Responsible animal welfare is a top priority for Burger King UK and we work very closely with our suppliers to ensure that all animals reared for meat are well cared for and treated. We require our meat suppliers and their producers to support the principles of the globally recognised Farm Animal Welfare Council Five Freedoms.”

A spokesperson for McDonald’s said: “We are deeply committed to the health and welfare of all animals in our supply chain and know that our customers expect us to uphold high standards. Together with our suppliers, we work hard to focus on continuous improvement and have led the industry with positive moves on chicken welfare. For example, three years ago we made a progressive change to increase the daylight provision and enrichment for all birds in our supply chain for all chicken served in our UK and Irish restaurants, providing pecking objects and perches to encourage the birds to express their natural behaviours. These steps meet higher welfare scheme requirements and are ahead of many of our competitors.

A spokesperson for Pizza Hut said: “We take animal welfare extremely seriously and have stringent policies in place to ensure all our suppliers adhere to the highest standards. We are also taking steps to ensure we continue to progress in this area – we support the European Chicken Commitment and as such we will expect our suppliers to meet a series of set requirements for all of the chicken in our supply chain by 2026. In addition to this, all our eggs are now free range, which is something we worked to achieve a year ahead of our target.”

KFC said: “We know our customers care deeply about chicken welfare standards and our business depends on it. We were proud to be one of the first restaurant brands to sign up to the Better Chicken Commitment but we won’t stop there. This is just the beginning and we hope others take confidence from our commitment and join the growing movement to create real change to improve the lives of chickens.”

Nando’s said: “We take animal welfare very seriously, knowing it’s as important to our customers as it is to us. We know that as a recognisable chicken restaurant group we have a responsibility to ensure that every aspect of how we source our chicken is done in the best possible way. We welcome initiatives like the Better Chicken Commitment and share the aspiration and recognition of the need to change, which we believe needs to be a combined effort across the industry. We look forward to keeping everyone updated on our plans as we move forward on this important issue.”

Domino’s Inc and Starbucks have been approached for comment.