A dessert containing more than 400% of a child's daily sugar allowance and a side salad with ingredients from 32 different countries were among the most surprising findings of secret diners.

The Soil Association's campaign Out to Lunch has created a league table ranking children’s food in 25 of the UK’s most popular restaurant chains in collaboration with Hugh Fearnley-Whittingstall and an army of secret diner families. Jamie’s Italian topped the table and Burger King came last.

The campaign found restaurants serving oversized children’s puddings with one pudding at Hungry Horse containing 78g of sugar, over 400% of a child’s daily sugar allowance.

Restaurants were found serving potatoes grown in Egypt, apples grown in Canada and a side salad containing ingredients sourced from 32 countries including Madagascar, Russia, Malaysia, Argentina, Bulgaria, Nigeria, Turkey, India and Peru.

Children’s meals were found to include additives linked to hyperactivity (E133 Brilliant Blue FCF), additives made from insects (E120 cochineal) and flavour-enhancer MSG (monosodium glutamate).

Despite continuing poor practice, the Out to Lunch league table shows that children’s food on the high street has undergone notable improvement since the campaign launched in 2013. There are now 13 chains now serving a portion of veg or salad with every meal (up from 6 chains in 2013) and 12 chains that include organic ingredients on the menu (up from 4 chains in 2013).

Rob Percival from the Soil Association said: “Thanks to our secret diner families, Out to Lunch is transforming children’s food on the high street – many restaurants are now prioritising child health and investing in healthier and more creative meal options. But there is still a national scandal unfolding in plain sight: 75% of UK parents say they are worried by the portion size of children’s puddings when they eat out. We found that renegade chains are ignoring parent concerns by dishing up super-sized calorific junk, undermining national efforts to tackle childhood obesity.”

The campaign also discovered the most calorific pudding on the league table. The Harvester’s Chocolate Cookie Pizza is a cookie topped with chocolate sauce, marshmallows, strawberries, butterscotch sauce and chocolate buttons, which contains 721kcal. This is more than triple the target set by Public Health England and represents almost 50% of a 7 year old’s daily calorie requirement. In response to the campaign, Harvester has committed to reformulating the pudding.

It also found that Jamie’s Italian, Wahaca and Nando’s are the only chains serving 100% British meat and Jamie’s Italian, Wahaca and Strada are the only chains serving higher-welfare (organic or RSPCA) meat.

The Out to Lunch campaign is calling on all high street restaurants, pubs and cafés to take seven simple steps to improve the service and food they offer children:

• Serve two portions of veg with every child’s meal

• Ensure children’s puddings are an appropriate portion size

• Make water freely available and stop promoting sugary drinks to children

• Offer children’s portions of adult dishes

• Offer quality ingredients such as free range and organic on the children’s menu

• Provide children’s cutlery as standard

• Make breast feeding mums feel welcome

An interactive league table featuring a profile of each chain can be viewed at soilassociation.org/outtolunch