It’s sometimes suggested that there might be future transfers of power from Member States to the EU, as part of the developing single currency project (perhaps following the so-called ‘Five Presidents Report’ on this issue) or for some other reason.

However, the UK has control over these developments. First of all, the UK has an opt-out from the single currency, as discussed below. Secondly, it also has a veto over future Treaty amendments.

But there’s more.

The European Union Act 2011, first mentioned above, also gives control to the British public over any significant Treaty amendment, by means of a referendum. This would apply where the UK would drop nearly any veto. It would also apply to other transfers of powers to the EU from the UK, defined in detail as including:

1. a) ‘the extension of the objectives of the EU’;
2. b) any ‘conferring’ or ‘extension’ of any EU competences, including over ‘the co-ordination of economic and employment policies’ (an issue in the Five Presidents’ Report), or;
3. c) giving any EU ‘institution or body’ any power to give orders or impose sanctions upon the UK.

It’s been suggested that the UK gave up a veto relating to single currency and banking issues as part of the renegotiation deal. This isn’t true, as the deal didn’t amend the Treaties and Parliament has not amended the 2011 Act.

So the UK’s control over any transfer of power from the UK to the EU is threefold: the UK government, UK Parliament and the British public.

Source: EU Law Analysis: EU Referendum Briefing 1: Can the UK control the EU’s future if it stays a member?