The charity Sense about Science has published a report called "Making sense of radiation: a guide to radiation and its health effects."
On power lines and EMFs, it says:
"Pylons and EMFs have not been established as a cause of childhood leukaemia. Laboratory trials using animal models and other tests have found no biological mechanism to explain how EMF exposure from power lines could cause cancer."
Sense about Science describe themselves thus:
"Sense About Science (www.senseaboutscience.org) is an independent charitable trust that responds to the misrepresentation of science and scientific evidence on issues that matter to society. We work with scientists and civic groups to share the tools and insights of scientific reasoning."
Powerwatch have posted a critical commentary on this report.