Many of the UK’s most popular tourist attractions are failing to serve up healthy meals and snacks for young visitors, instead largely selling pre-prepared children’s lunchboxes loaded with sugar along with chips and “unimaginative, ultra-processed” foods, according to new research by a charity.

The Soil Association’s annual Out to Lunch survey found that 75% of lunchboxes sold at popular attractions did not routinely include a portion of vegetables or salad, while half included muffins, cakes and sweet treats but no fresh fruit.

Millions of families visit the UK’s main visitor attractions during the school holidays. Yet a poll by the charity showed that only 14% of parents said they thought the children’s food on offer was good enough.

The charity and organic certification body, which supports sustainable food and organic farming in the UK, surveyed the food and drink on offer at 20 of the UK’s most popular family attractions, covering all English regions, Scotland, Wales and Northern Ireland and ranking them in an online league table. Research was undertaken covertly by parents, as well as via desk-based menu reviews and a questionnaire.

London’s Natural History Museum and Brighton Pier scored joint last place in the league table, while the Eden Project in Cornwall topped the rankings, with Chester zoo in second place. When it came to sustainability and sourcing, only three attractions – Eden Project, Chester zoo and Durham cathedral – could reliably tell parents where their meat came from.

“Visitor attractions are making life hard for parents who want to enjoy a healthy and happy day out,” said Rob Percival, Soil Association policy officer. “Lunchboxes loaded with sugar and unimaginative ultra-processed foods are the norm and also a missed opportunity. So long as junk-filled lunchboxes continue to dominate family outings, parents will have a hard time convincing their children that healthy food can be a treat too.”

A lunchbox at London zoo was found to include up to 36g of sugar – 189% of a child’s daily sugar allowance – for example, while kiosks in the zoo sell fizzy drinks at a cheaper price than water.

Of the good practice highlighted in the survey, Chester zoo served locally sourced milk and farm-assured meat, while all meals at the Eden Project were freshly prepared and included locally sourced meat and vegetables.

“Good food is at the heart of the Eden Project experience,” said Andrew Holden, the Eden Project’s purchasing director. “We make sure that meals are freshly prepared and that our ingredients are responsibly sourced, fairly traded, organic, local, and seasonal.”

Parents reported that while sugary and fizzy drinks were readily available, few attractions were prominently providing free fresh drinking water for children.

Anya Hart-Dyke, an Out to Lunch secret diner parent, commented: “I’ve lost count of the lunchboxes and children’s meals we’ve encountered on family days out that I just won’t consider buying for my child. Healthy, real food must be a priority for family attractions – I’d be far more likely to come back if I knew my child would get some proper food.”

The survey found some of the most popular attractions serve some of the worst food – the five bottom-scoring attractions receive 4.5 times as many visitors each year, compared with the five top scoring venues. The majority of attractions offered healthier adult food, compared with options for their children.

The Natural History Museum, which attracts 5 million visitors a year, said in a statement: “As a museum we help inform choices for society to create a sustainable future. Our restaurants and cafes are run by Benugo, who exceed standard practice for ingredients’ provenance, welfare and farm assurance, and seasonality. We look forward to engaging more fully in the survey next year and are confident that our high standards will result in a better ranking.”

Anne Martin, managing director of Brighton Pier, questioned the the survey results, saying the attraction had not received the questionnaire. “Accordingly, the survey results are inaccurate and unrepresentative of the efforts we have made to offer our customers a choice of healthier, sustainable dining options. The children’s menu in Palm Court was at the forefront of Jamie Oliver’s recent national Sugar Smart campaign when it was launched in Brighton, offering reduced sugar items to children: we have received many compliments for this as a result.”