Not true. 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! Evidence
If you want more details, including the distinction between directives and regulations, as well as why the whole method of just counting laws is fairly meaningless anyway, there’s an in-depth report provided by the independent factcheckers FullFact.