The independent House of Commons library found that the real proportion is just 13.2% of our laws. And these figures include everything that even mentions the EU, even if it's just a passing reference or a definition, according to the researchers!
Broken down this means 1.4% of our Acts of Parliament and 12.9% of implementing measures (Implementing Measures are mandatory requirements in the form of regulations which come into force without further implementation into national laws.)
Hardly overwhelming, is it? http://www.richardcorbett.org.uk/laws-from-brussels/