Parents in Bristol are being asked to put their children forward so new swine flu vaccines can be tested on them.

They are being invited to apply through a website for the trial.

Their children will each receive two jabs and the effect will be studied by experts from Bristol University.

They want to establish which of the vaccines works best and to check if there are any side-effects.

The first youngsters will be given the inoculations at Bristol Children's Hospital from next week as part of the study.

A total of 250 children in the South West aged six months to 12 years will be given the vaccinations, with the bulk expected to be from Bristol.

Professor of paediatrics at Bristol University, Adam Finn, is leading the project in the city.

He said: "Children are one of the age groups most vulnerable to swine flu infection, so it is vital that we obtain information on their response to these vaccines. This study will help in decisions about which vaccine will be best for protecting children.

"We will be checking for sore arms and fevers but the key thing is to look at the antibodies within the blood.

"These are the vaccines we expect to be using within a few weeks. They are very similar to vaccines that have been used in studies and in people for many years.

"We would not be doing a study if we thought we were putting children at risk, and nor would the Government be buying and distributing the vaccines if they thought they were dangerous."

Millions of doses of two swine flu vaccines have been bought for use in the UK by the Department of Health to control the expected outbreak this autumn.

The vaccines have already been tested in adults but more information is needed about how they work in children.

When the vaccination programme begins later this autumn youngsters and adults with long-term health conditions will be given priority.

But the study will help experts decide whether more youngsters should be given the inoculation against the H1N1 virus.

A website has been launched to provide parents with more information about the research and to advise them how to take part in the study.

Youngsters who take part will be given the vaccine on their first visit to the children's hospital along with a blood test with local anaesthetic, and will then return three weeks later for the second jab. A further six weeks later another blood sample will be taken so that scientists can determine how well the vaccine has worked.

Parents will be asked to fill in details of any reactions or side-effects their children suffer and if they need to visit a doctor or the hospital following the vaccine.

The project is a collaboration between University Hospitals Bristol NHS Foundation Trust, Bristol University, Oxford University, University of Southampton Wellcome Trust Clinical Research Facility, St George's Vaccine Institute in London and the Royal Devon and Exeter NHS Foundation Trust.

The parents of children taking part in the study will be given a 24-hour helpline number to contact if they have any concerns.

Parents interested in enrolling their child in the study should call 0117 342 0699 for further information.