Giving schoolchildren free fruit to improve their diets may not have any long-term health benefits.

A report by experts claims that once pupils are older, and no longer eligible for the free fruit in schools scheme, any boosts their bodies get from nutrients and vitamins evaporate.

The report comes as the Scottish Executive launches a £5m pilot extension to its free fruit scheme with primary one to three pupils in the Borders, East Ayrshire, Fife, Glasgow and West Dunbartonshire being given free nutritious meals during a six-month trial. Since 2004, the government in Westminster has spent £119m providing all four to six year-olds with a piece of fruit every school day. The scheme has been running in Scotland since 2003 at an estimated cost of £2m a year, setting the template which was replicated south of the border the following year.

However, according to a study published today in the Journal of Epidemiology and Community Health, once pupils are older and no longer eligible for the free fruit in schools scheme the benefits could not be seen at all.

Epidemiologist Professor Janet Cade and colleagues assessed the impact of the School Fruit and Vegetable Scheme on 3700 primary one and two children from 98 schools in the north of England during 2004. The results showed the scheme initially boosted fruit intake by half a portion and slightly increased levels of beta carotene and vitamin C.

However, these increases had waned seven months later and had disappeared completely by the time the children reached primary three and were no longer eligible for the scheme.

There were no changes in salt, fat or overall energy intake among the children.

Fruit and vegetable intake actually fell at home, possibly because parents thought their children were getting their quota at school.

The executive said its own research refuted Ms Cade's findings.

A spokeswoman said: "We carried out our own evaluation in 2005 and 90% of respondents now eat more fruit and vegetables than they did."