7%?
I would suggest that Nick Clegg is quoting from this study that states that the EU accounts for 6.8 % of primary legislation and 14.1% of secondary legislation.
www.parliament.uk/briefing-pap...
It then goes on to state the following:
"Problems with the calculation
These figures are indicative of the impact of EU legislation on
national law-making but they are not the full story. For example, they
do not take account of EU “soft law” or the overwhelming majority of EU
regulations, which can be several times the number of directives (see
tables on page 12), and which are usually adopted in the Member States
by measures other than laws."