People are making progress on cutting their salt intake but too many still forget to check for hidden salt in foods, campaigners warn.
Pizza may contain hidden salt
Three-quarters of the salt we eat is already lurking in the food we buy, says the Food Standards Agency.
Sandwiches, ready meals, pasta sauce, and pizza are some of the biggest sources of "hidden" salt, it says.
The agency's next round of TV ads, launched on Monday, shows consumers how to check food labels for salt content.
Salt levels can vary considerably from product to product and there is always a lower salt option, says the FSA.
In the UK, bread, breakfast cereals, biscuits, cakes and meat products such as bacon, sausages and ham are some of the main sources of salt in people's diet.
Yet only 40% of people check the label for salt content when buying food, according to a poll of nearly 2,000 British adults.
And just 14% of those asked correctly said that a pack of food with 1g of sodium contains more salt than one with 1g of salt.
More than half of the respondents (59%) mistakenly believed that both packs contain the same amount of salt.
Four in 10 claimed to be making a special effort to cut down on salt in their diet - an increase of 18% since the FSA's salt reduction campaign began in 2004.
Foods where some brands/recipes are high in salt
However, 90% of these said that they were cutting down by not adding salt to their food - with only 15% saying they checked labels and 12% saying they were eating less processed food in order to reduce their intakes.
Latest data show daily salt consumption is going down - the average is now 9g, down from 9.5g in 2001.
But more work is needed to reach the ideal 6g target the government has set for 2010, says the FSA.
Check the label
FSA chair Dame Deirdre Hutton said: "To help achieve this, the FSA will continue its work in encouraging industry to offer consumers healthier choices and to encourage consumers to drive demand for those healthier choices."
Betty McBride of the British Heart Foundation said: "There is too much salt lurking in processed food. You can't always taste it, and sometimes it is in the most unlikely products.
HIGH OR LOW
HIGH -1.25g salt or more per 100g (0.5g sodium or more per 100g)
LOW - 0.25g salt or less per 100g (0.1g sodium or less per 100g)
If a figure is for sodium, multiply the amount eaten by 2.5 to find the amount of salt
"It can cause high blood pressure and increase your risk of heart disease - so we've all got to become detectives on the trail of this hidden killer.
"By simply checking the labels and switching to a lower salt option, you'll be doing your heart a favour."
Public Health Minister Caroline Flint said: "Increasing consumer awareness is an integral part of driving the market towards lower salt options, and complements our partnership work with the food industry to deliver across the board salt reductions."