Parents should also be warned against favouring the less effective single jabs over the combined MMR jab.
The study of 14,758 UK children revealed that 88.6 per cent of children born between 2000-2002 had been immunised with the MMR jab by the age of three.
This is below the level required for herd immunity, over 95 per cent, and has resulted in an increase in cases of measles.
A total of 970 cases of measles were confirmed in 2007, compared with 740 in 2006.
The study also showed that three quarters of the parents who chose not to have their child immunised with the MMR vaccine did so because of concerns over the links to autism and the negative media attention.
Lead researcher Dr David Elliman, a consultant in community child health at Great Ormond Street Hospital in London, said: 'GPs should take every opportunity to give the MMR jab to children whenever they present at the surgery.
'They must be confident that they can answer any questions raised by concerned parents and be aware of the latest evidence supporting MMR.'
Dr George Kassianos, RCGP immunisation spokesman and Berkshire GP, said: 'The problem is that parents who do not want their children to be vaccinated do not come to see their GP.'
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