NHS Direct was established five years ago

The study suggests it is rarely used by those who would arguably benefit most from advice from nurses.

These include the poor, the elderly and those from ethnic minorities, who generally suffer more ill-health.

However, the Department of Health disputed the findings saying the helpline is used by people in a wide variety of social groups.

NHS Direct was established five years ago and was heralded as a way of reducing pressure on GPs and A&E departments across the country.

According to the Department of Health, the helpline receives 500,000 calls per month. Studies have shown that the service is popular with people who use it.

Not calling

However, this latest study, which was funded by the Economic and Social Research Council, suggests many people who could benefit from it are not using it.

NHS Direct's own research... found a wide range of socioeconomic groups use the service Department of Health spokesman

Professor Gerard Hanlon of the University of Leicester, studied callers to two large NHS Direct telephone centres.

He found that most users are white, middle class and aged between 30 and 60.

He found that men in this group use NHS Direct for themselves, their partners and relatives, including children and parents.

It is also popular with new parents, many of whom prefer it to their local GP because of fears the doctor might regard their query as trivial and a waste of time.

The over 60s and the under 20s are least likely to call the helpline.

Findings criticised

The Department of Health rejected the findings.

"This is a small-scale study," said a spokesman.

"NHS Direct's own research analysing call data over a six-month period from three sites found a wide range of socioeconomic groups use the service.

"It is only people from the most extremely deprived social groups and the most privileged groups who use the service less."

The helpline started another study last month to identify how many people from ethnic minority groups use the service.

The spokesman said: "While it is far too early to draw firm conclusions from this, early indications suggest that NHS Direct is well used by callers from a range of different ethnic backgrounds, reflecting the balance of the local population."

The findings will be presented at a conference at the University of Leicester on Monday.