The salt content in most foods has gone down but has risen in ready-made sauces  by an average of 15% since 2011, according to research by government food safety inspectors.

Tomato puree, tinned tuna and jars of red cabbage and apple also contain more salt than five years ago, the NVWA said in a new report on Wednesday.

However, the salt content of crisps, most tinned vegetables and legumes, cheese, bread and read-made meals has gone down by an average of almost 7%. The NVWA tested over 1,000 products covering 10 product groups.

The research also shows wide differences between different manufacturers. One type of tomato sauce contained 1.1 grammes of salt per 100 grammes while another had more than double, the NVWA said. Curry sauces, sate and mustard show similar differences.

The NVWA monitors the salt content of food as part of government efforts to get manufacturers to reduce salt levels. The officially recommended daily maximum is six grammes a day.