But ministers fear that some plans, such as a banking union, could change the rules of the single market through the back door. Cameron believes he can block distasteful proposals by wielding the British veto. That is what he did in December when he blocked a German-led attempt to embed the eurozone‘s fiscal compact in EU treaties. After the British veto the 17 eurozone members persuaded a total of 25 of the EU‘s 27 member states to sign a non-EU treaty.