ThatBritGuy:

Then have an official explicit EU-wide referendum.

We have advocated this here, but we have also realised that setting up the EU in that way (or in any number of other ways) would require its own treaty and referendums. And the sovereigntist opposition would be much louder especially in small states because  agreements passed by a qualified majority of an EU-wide popular vote would be more legitimate.

Time for me to peddle my mini treaty again?

1. The EU bill of rights (Title II of the current treaty).
2. Union membership rules (Title  IX of the current treaty, including Article I-60 on Voluntary withdrawal from the Union)
3. The 2009 European Parliament will be a constitutional assembly
4. Referendum rules: The treaty shall be put to a vote by referendum simultaneously in all EU members states.

The result of the referendum will be binding if at least 50% of all EU citizens cast a valid vote in it.

The treaty shall come into force only if at least 50% of valid votes in a binding referendum support the treaty. In that case,

• An EU member state shall be considered to have approved the treaty if it is supported by at least 50% of valid votes in that member state, and the number of valid votes in that member state is at least 50% of the eligible voters.
  
• An EU member state where the treaty is not approved shall hold a second referendum within 5 years, with the choices being approval of the treaty or withdrawal from the EU according to the provisions of the treaty.
  
• A transitory institutional regime shall apply as long as there are any remaining EU Member States which have not approved the treaty and have not yet held a second referendum.

This will have to pass by referendum or parliamentary vote in all member staes, won't it?

When the capital development of a country becomes a by-product of the activities of a casino, the job is likely to be ill-done. — John M. Keynes