By 2008, it will be illegal for workers to be exposed to electromagnetic fields higher than 300GHz.
Experts are concerned the new laws will mean pioneering advances will be banned and patients, particularly in vulnerable groups such as children and those with cancer, will miss out on best treatment.
MRI scanners use magnetic fields to build up a picture of the inside of the body. The stronger the magnetic resonance, the more accurate the image.
Experts have always been aware there is the potential for side effects and risks with their use.
Professor Mansfield says the legislation is based on "very uncertain science" and warned it could lead to a medical brain drain, with experts moving to work in the U.S. where the rules are not so strict.
The Food and Drugs Administration sets an MRI exposure safety limit for patients that is 1,000 times higher than the level proposed for MRI operators by the EU.
