Earlier this week, George Osborne, UK Chancellor for the Exchequer and alleged Prime Minister-in-waiting, made demands for EU treaty change to protect the City of London from Eurozone-led discrimination.
The calls come as Britain seeks to reform and renegotiate its relationship with the EU ahead of its membership referendum, likely to be held next year.
Osborne, in an interview with the New Statesman, voiced concerns over the relationship between Euro and non-Euro countries, questioning Britain's ability to coexist in a single market where the Eurozone area has the ability to determine common rules.
He highlighted this as his single biggest concern regarding the UK's continued membership of the EU, saying, "The EU was not designed to accommodate two classes of members, where one group is rapidly integrating to try to make the single currency work, and the other group, particularly Britain, doesn't want to be part of that ever-closer union. And our treaties don't provide for that."
He went on to add that the only foreseeable solution to the problem must be, "things that are legally binding and irreversible and, therefore, almost certainly treaty change." Without such change, Osborne went on, "British membership is going to become increasingly difficult."
Whether treaty change is achievable is open to debate, though it is unlikely to occur before the referendum.
Results of the negotiations have so far been kept under wraps, though David Cameron, the UK Prime Minster, said "significant progress" had been made.
Yesterday, Jean-Claude Juncker, the European Commission President, in his state of the union speech specifically addressed the issue saying, "we must preserve the integrity of all four freedoms of the single market while finding ways to allow the further integration of the Eurozone to strengthen the economic and monetary union."
This may bring cause for optimism for Osborne and fellow reformists, though treaty change is difficult to achieve, as all 28 member states must ratify any amendments before they are accepted.
In May, French Europe Minister Harlem Désir said, British renegotiation "has to be done without amending treaties, I think the British know this. There would be strong opposition in the majority of states."
When questioned on the matter, British MEPs largely supported Osborne's calls to protect the City of London from discrimination while reiterating that change must come as part of a wider package of reforms.
Catherine Bearder, a member of the Alliance of Liberals and Democrats for Europe said, "when treaty change is on the table, the non-Eurozone countries will need some form of reassurance they won't be discriminated against," though she noted that "treaty change isn't going to happen any time soon."
Ashley Fox, leader of the Conservative UK delegation and a member of Parliament's European Conservatives and Reformists Group, offered more explicit support for Osborne, "One of our key renegotiation platforms is our call for fairness - especially when it comes to the relationships between Eurozone states and Euro out countries such as ours.
"It is important that we protect the City and British commerce from potential ganging up by the Eurozone."
"We are looking for a range of reforms. Some may need treaty change and some can be achieved without it. I fully support the Chancellor when he proposes an ambitious menu of potential reforms and along with the other Conservative MEPs I will be doing all I can to help him deliver them."
Jean Lambert, member of the Greens/European Free Alliance Group, also backed the proposal, saying, "George Osborne is right that the relationship between those within the Eurozone and those who are not needs clarifying and may need a treaty change."
However, she issued a reminder that success treaty change will largely, "depend on whether or not the UK really wants to participate in the non-currency issues," referencing the current refugee crisis as a case in point.