The debate about mobile phone safety has raged for years.
More research is to be carried out into mobile phone use
A series of confilicting reports has led to suspicions mobile usage and the accompanying base stations may harm health and increase the risk of cancers.
The UK's biggest investigation into mobile safety has now drawn up its own conclusions.
What is the latest study?
The UK Mobile Telecommunications and Health Research Programme was established in 2001 on the recommendations of the independent government-commissioned report chaired by Sir William Stewart.
The £8.8m programme has been jointly funded by government and the industry, although it has an independent management committee.
Members mainly include university academics.
The first of the 28 research projects into mobile phones, base stations and masts started at the end of 2001 and to date 23 have been completed.
What health effects have mobile phones been linked to?
Fears have been raised about a number of possible adverse effects to health.
The highest profile consequence, some research has suggested, has been an increased risk of brain and ear tumours.
But there have also been claims that radiofrequency fields affect brain function, which could lead to problems with blood pressure and heart rate.
And some argue that they are responsible for electrical hypersensitivity, sufferers of which report headaches, dizziness and tingling.
They attribute these problems to devices such as mobile phones, base stations, computers and televisions.
The 2000 Stewart report concluded that mobile phones did not appear to harm health, but recommended further research was carried out.
And in 2005 Sir William added that mobile phone use by children should be limited as a precaution - and that under eights should not use them at all.
Does the latest report give mobiles a clean bill of health?
It does rule out short-term effects to brain function and links to electrical hypersensitivity and says further research is now not needed.
But on the issue of cancer, it is more ambiguous. No evidence of a greater short-term risk was found - but researchers said the problem was that cancers do not generally emerge until 10 to 15 years after the event.
There were very few people in the study who had been using mobiles for longer than 10 years, the researchers said.
But they added those that had did show a "hint" of an excess risk, although this was only on the borderline of statistical significance.
Base stations were not looked at in as much detail as mobile phones.
But researchers said radio frequency exposure is much lower - although there are problems measuring this exactly as it depends on where they are sited - and there are no health risks.
The programme did not look at mobile phone use in children. Researchers said at the time mobile phone use by children was less common than it is now and there were ethical concerns about testing children.
What is happening next?
The programme has been given over £6m to expand its remit. It will now look at the effect of mobile phone technology on children as well as carry out longer term studies on the risk of serious disease.
This will include looking for links to cancers and degenerative conditions such as Alzheimer's and Parkinson's.
The research is likely to involve over 200,000 people and include researchers from Denmark, Finland and Sweden as well as the UK.
What is the advice on mobile phones?
Professor Lawrie Challis would not be drawn on whether people - and in particular parents - should restrict mobile phone use.
He said it was up to the government to offer advice, although in previous media interviews he has warned about letting children use them.
The Department of Health said the precautionary principle set out by Sir William still stands.