Food manufacturers are hijacking the Government's message about eating five portions of fruit and vegetables a day as a new tactic to sell their products, independent experts will claim this week.

Ministers, worried that there is growing consumer confusion over healthy food claims, have asked a panel of experts to clarify exactly what constitutes a fruit or a vegetable.

Food campaigners will tomorrow produce a report hitting out at some major manufacturers for their food labelling. Tinned spaghetti, fruit drinks and soup are all being given promotional labels suggesting that they are as healthy and nutritious as fresh fruit or vegetables, although they contain salt or sugar.

Heinz is marked out as a culprit for describing a small tin of spaghetti and sausages as being 'one portion of fruit or vegetables'. The tin also contains 2.5 grams of salt - nearly the maximum amount of salt (3g) a seven-year-old child should eat in a day.

Knorr, part of the Unilever Bestfoods group, has a new range of 500ml Vie Soups, which are sold as the equivalent of two portions of vegetables. A spokesman for the company said: 'It is a processed product but this is an easy and accessible way for consumers to get their required quantities of vegetables, as part of a balanced diet.'

However, the Government's own guidance states that some processed foods 'are unlikely to contain sufficient fruit and vegetable ingredients, for example, ketchup, processed vegetable soups, fruit cakes and yoghurts.'

Sainsbury's produces a smoothies drink in its Way To Five range, targeted at consumers who want to get five portions a day. It claims that its drinks contain the equivalent of three portions of fruit, although Department of Health guidelines state that fruit juices only count as one portion of fruit a day.

A spokeswoman for the supermarket chain said the claim was based on the amount of crushed fruit in each drink. As 80g of fruit counts as one portion, drinks which use 240g of fruit in each bottle therefore have three portions, she said.

But the claims have angered Sustain, the food and farming campaign group, which believes the labelling is duplicitous. Jeanette Longfield of Sustain said: 'It is outrageous that companies can suggest that spaghetti with sausages is equivalent to a fruit or a vegetable.

'These companies are cynically hijacking the health benefits of fruit and vegetables, and confusing consumers in the process. The Government needs to state, quite clearly, that processed products with high levels of salt, fat or sugar cannot count towards the five portions of fruit and veg we need to eat daily to keep us healthy.'

The five fruit-and-veg-a-day rule is based on World Health Organisation guidelines.

The Government has promoted it as part of their £40 million campaign to try to combat the increasing incidence of obesity, particularly among children and teenagers who eat on average just two portions of fruit and vegetables a day.

A spokeswoman for the Department of Health said last night: 'We are drawing up detailed nutritional and technical criteria to clarify the foods which count towards the five-a-day message. We will publish these shortly to ensure greater consistency of the message.' She added: 'Many processed and composite foods which contain fruit or vegetables, such as pasta sauces, convenience meals and prepared desserts, may also contain fat, sugar or salt.

'The recommendation to eat more fruit and vegetables is an important one, but this needs to be considered in the context of advice to reduce consumption of fat, salt and added sugars as part of an overall balanced diet.'