Mobile phones are not linked to health problems when used for 10 years or less.
But further research is needed into their longer-term impact and their effect on children, a report says.
A six-year research programme found no association between mobile phone use and brain cancer nor evidence of brain function being affected by mobile phone signals.
But the impact of mobile phone use after more than a decade is less clear, according to the Mobile Telecommunications and Health Research Programme (MTHR).
Cancer symptoms are rarely detectable until 10 to 15 years after the cancer-producing event so it is too early to "say for certain" whether mobile phones could lead to cancer or other diseases such as Alzheimer's and Parkinson's, the report said.
Further research into the the impact of mobile phone use on children is also needed because it is possible they may have different or stronger reactions to mobile signals than adults, the MTHR recommends.
The MTHR's £8.8 million research programme was set up in 2001 with funding from a variety of Government and industry sources. It has funded 28 research projects of which 23 have been completed.
Wednesday's report summarises those project findings, most of which have already been published in scientific journals.
MTHR chairman Professor Lawrie Challis said: "The results are so far reassuring but there is still a need for more research, especially to check that no effects emerge from longer-term phone use from adults and from use by children."
None of the studies found any evidence that exposure to signals affected brain function.
