The pizza chain’s saltiest dish was found to be the Napoletana, which served up 9.6 grams of salt per serving, followed by Barburrito’s beef wrap with nine grams and Wetherspoon’s gammon and eggs with 8.8 grams.

ASK Italian's risotto pescatore (8.6 grams), Beefeater's mixed grill (8.1 grams) and Harvester's mixed grill (8.01 grams) were also found to be high salt culprits. The table below highlights 13 restaurant chain's meals with the highest salt per serving.

Italian food, street food and pub food were the cuisine's most regularly featured in the highest salt ratings, with Japanese and seafood also picking up a mention.

However, Burger King’s Whopper and regular fries, only had a salt rating of 3.7 grams per serving in comparison, almost three times less than the PizzaExpress dish.

The second saltiest fast food dish was KFC’s fully loaded box meal with 3.44 grams of salt and Domino’s personal pepperoni passion pizza with 3.35 grams came in third.

The daily recommended salt intake for an adult is two to six grams a day, meaning many of the options when eating out hit or exceed that intake.

Dr Wayne Osborne, who conducted the research for treated.com, said: “Most people associate a high salt diet with an increased risk of high blood pressure and heart disease, and they’re right to. Along with being overweight, excessive alcohol consumption and smoking, eating too much salt is one of the leading causes of hypertension. This can of course be a precursor to heart disease and stroke.

“For adults, staying within the 2-6 gram range greatly reduces the risk of these conditions developing. But as we’ve seen, when eating out, remaining within this safe threshold can be a challenge, particularly in those cases where the nutritional info is not readily available.

“When dining out, consumers should also not be afraid to talk to their server and see which less salty options are available to them. Many restaurants who prepare their food to order will be willing to use less salt in a dish upon request.”

Osborne however found some chains offering very low salt offerings, including PizzaExpress which Leggera Superfood Salad contains just 0.8 grams of salt, containing less than 10 times the salt levels of the pizza.

YO! Sushi’s tuna sashimi contains just 0.1 grams of sale and ASK Italian’s spaghetti Bolognese contains just 0.3 grams of salt.  Other low salt options came from wagamama’s sirloin and shitake salad, Wetherspoon’s salmon salad and Harvester’s veggie chilli burger.

Osborne called on restaurant chains to high street restaurant chains to reveal the nutritional information of their meals in a similar way that fast food chains are forced to do.