I believe that a study made by the Germans calculated that 80% of their legislation emanated from EU diktats - whereas the House of Commons Library concluded, that it is “possible to justify any measure between 15% and 50% or thereabouts, depending on the approach.”
We've probably done this more than once. I might just make a "blog" page of this post just for the information it makes reference to.
I personally think the most believeable view is that put by "Full Fact" which does indeed conclude by stating the very words you have, taken from the same House of Commons Research Report.
The opening paragraphs of their page show how exactly how Clegg pulled his "7%" mendacity. He was quoting Polly Toynbee's calculations from The Guardian in 2011.
Full Fact make reference to the fact that "legislation" means
(a) UK Acts of Parliament, "Primary Legislation", Bills that go through the full cycle ...
(b) Statutory Instruments, secondary legislation passed without "full debate" in the house, as for example the shoddy recent attempt by George Osborne to screw over the element of our society dependent on welfare, rightly shot down by the House of Lords, but also exploited many times by Blair, including his placing of hanging beyond use as a punishment in the UK ever again (clear self interest there I feel), and ...
(c) "Regulations" made by the EU which are immediately enforceable in UK law without further action by our so called "Sovereign" parliament. John Major had a word for the need for legislation to be done at the EU only if it could not be done locally, and that national parliaments should have a final say and veto. Can't remember what that word was but it must have been something related to circus performers and trapeze artists in particular as what we have got is the exact opposite.
"According to the House of Commons Library document, from 1980 to 2009, 186 out of 1302 UK Acts (14.3 per cent) “incorporated a degree of EU influence”. If we exclude those Acts which only included “passing reference” to the EU, this proportion reduces to 10.1 per cent. Polly Toynbee’s claim seems to be based on a shorter time frame, from 1997 to 2009, during which time 6.8 per cent of primary legislation “had a role in implementing EU obligations”."
So there's Clegg's 7% claim, right there. And a right pile of stinking obfuscation of the truth it is.
As I said in my opening above, the claims for a higher degree of involvement can be justified in various ways, and I think the Full Fact team have done a decent job of putting together a summary of what the spread is, and gone quite a way to explain why there is such variation (such as the inclusion by the europhobes, and exclusion by the europhiles, of Regulations that have no Regulatory Impact in this country, such as for example the regulations governing production of Olives and Olive Oil).