More than three-quarters of museums, galleries and other attractions in the UK are giving £65m of ticket-price concessions to the over-60s every year, while in many cases young people are charged full-price tickets, according to a study.

People over 60 are offered concessions regardless of their ability to pay and even when they are below the state pension age, according to the Intergenerational Foundation (IF), a charity that researched 35 of the UK’s leading attractions’ ticketing policies.

The giveaway to older people is expected to fuel concerns that Britain has failed to adjust to growing pensioner incomes and wealth. With millions of pensioners boasting incomes above the average wage, the IF said it was concerned that charging policies developed in previous decades were out of date.

While they all offer the over-60s senior discounts apart from RHS organisations, only four – Chester zoo, Stonehenge, Canterbury Cathedral and Bristol zoo gardens – have raised the ticket-price concession threshold in line with the state pension age (SPA) of 65.

Only one out of the 35 organisations offers a young person discount – the Royal Shakespeare and Swan theatres in Stratford-upon-Avon – although 27 offer student discounts.

Among the worst offenders are Scottish attractions Edinburgh Castle, the National War Museum in Edinburgh, Stirling Castle and Urquhart Castle, all of which offer an over-60s concession but no student or young person’s discount.

Chloe Wall, who co-wrote the report entitled Baby-boomer Concessions: How ticket prices for a wealthier generation reinforce unfairness, said: “At the very least these attractions should remove these concessions for those below SPA and introduce a student discount. Such unfair pricing practice sends a damaging message to young people that they are simply less valued and that cultural attractions are only for older people.”

The long-term squeeze on public funding in the arts and cultural sector has forced many organisations to increase ticket prices. In April, the National Gallery raised the cost of an exhibition ticket beyond £20 for the first time, charging £22 for its Claude Monet exhibition on weekends.

The concessions appear to assume that today’s over-60s are less well-off than recent graduates, which has not been the case in terms of income and asset wealth for the past 15 years.

“In the past, concessions were used to help poorer older people to be able to afford to participate in society’s cultural life, but our findings show that these are increasingly bungs to wealthy baby boomers,” said Wall.

The authors looked at the cost of tickets measured against disposable income and found that on average young people would spend 12% of their weekly disposable income, excluding travel costs, on a ticket, while the same ticket for people over 60, many of whom enjoy free local bus travel and discounts on public transport, would cost only 5.6% of their weekly disposable income.

The cost of these concessions would be enough to fund the running of at least 150 independent museums (£430,000 a year on average) and fund the equivalent of 1,500 jobs.

The UK lags behind other European countries: Italy has abandoned old-age discounts and France gives free admission to the under-25s but many cultural attractions in the UK continue to not offer discounts to the young.

Angus Hanton, the co-founder of IF, suggested that UK attractions replace all old-age concessions with free entry for those on pension credit, or they could introduce under-30s discounts. He added: “It is also quite possible that this discriminatory, age-based pricing is unlawful.”

The research found that students almost always have to produce a student card, whereas seniors are rarely asked to prove their eligibility.

• This article was amended on 19 September 2018. An earlier version said travel on public transport was free for people over 60. This has been corrected to free local bus travel and discounts on public transport. It was further amended on 17 October 2018 to clarify that the free local bus travel is not available to all people over 60; the qualifying age varies by location.