Bite Back 2030 has launched a report calling for an end to misleading claims in food marketing.
The youth-led group examined over 500 food and drink products with nutritional claims on its packaging, identifying 57 per cent as high in fat, salt and sugar (HFSS).
The figure rose to 62 per cent for drinks due to their high levels of sugar.
The organisation also surveyed 1000 teens aged 13 to 18 to examine the effect of “health halos” on young people across the UK.
The group reportedly found that 73 per cent of participants said that their diet is healthy, despite their intake of fruit, vegetables, sugar and fibre not meeting the government recommended guidelines.
Nine in 10 teenagers consider smoothies as healthy despite the 76 per cent of products which receive a red nutritional label for high levels of sugar.
Eight out of 10 teenager consider cereal bars to be health foods, while 81 per cent of available ranges contain levels of sugar high enough to receive a red nutritional label.
Teenagers also overwhelmingly believed that yogurts are healthy, despite 35 per cent of flavoured yogurts being given a red score.
“These findings are so shocking,” Bite Back 2030 youth board member Jacob said.
“Companies need to step up and be more honest and transparent with their audience, especially young people.”
Chairman of Action on Sugar and Salt Graham MacGregor added: “It is morally indefensible for manufacturers to mislead shoppers into buying and eating food that looks healthy on the outside of the packet, when it isn’t healthy on the inside.
“We are in an epidemic of childhood obesity, and we support Bite Back 2030’s call that this practice must end now.”