Mark Carney’s intervention last week in the debate over Britain’s relationship with the European Union was remarkable for two reasons.

The first was the Bank of England Governor’s apparent decision to move into overtly political territory. There was no problem with the bulk of his speech and the accompanying 100-page report which provided a sophisticated, rigorous and entirely appropriate analysis of the impact of EU membership on Britain’s monetary and financial stability.

But trouble lay in Mr. Carney’s assertion that future eurozone integration could pose a risk to U.K. financial stability and that the government therefore needed to secure safeguards, including recognition that the EU is a “multi-currency union,” as part of its much-trumpeted renegotiation.

Mr. Carney made this assertion using identical language to U.K. government ministers, who have recently seized upon protection of the City of London as its latest EU renegotiation priority. Yet there was nothing in the BOE report to support the claim that the U.K. is at risk from future eurozone caucusing, or to explain what form those risks might take; the statement simply pops up on the final page. For those skeptical that such a risk exists or that there is anything the U.K. government could usefully achieve to address it, the omission leaves the BOE open to the accusation that this was a politically driven exercise, thereby undermining its credibility.

That is unfortunate because what was also remarkable about the BOE’s report was just how compelling its evidence was that EU membership has been beneficial to the U.K. economy. The BOE drew on a large body of academic research to show that since joining the EU, the U.K. economy has become more open and more dynamic. Nor is this simply a coincidence, the happy result of a global trend toward greater openness and free trade.

The BOE identifies various indicators that show openness has increased notably faster across the EU than among other developed economies. This in turn has supported the economy by allowing more specialization, more competition, improved innovation and efficiency and greater economies of scale.

This is obvious to anyone who has observed European business and finance over the past two decades: Since the creation of the EU single market, the European corporate landscape has been dramatically restructured, shifting from an organizational model based upon ringfenced vertically integrated national subsidiaries to one based upon pan-European structures and supply chains. It should also be noted that this process, much of which has been organized and financed in the City of London, has delivered rich rewards to the U.K.

Indeed, Mr. Carney noted that by more fully embracing openness than most EU countries, the U.K. has arguably been the biggest beneficiary of the EU’s four freedoms—the free movement of goods, capital, services and people.

Of course, euroskeptics are entitled to ask why, if the EU is such a blessing, has its recent economic performance been so dire? The answer lies partly with the euro. Flaws in the design of the single currency meant that the openness and interconnectedness that delivered benefits during the boom became a liability during the crisis, allowing the faster transmission of shocks. In response, the eurozone has been forced to improvise new mechanisms to cushion shocks, share risks and limit contagion, including the creation of bailout funds, a banking union and new central bank tools. This risk-sharing needs to go further, with further pooling of both public debts via an expanded eurozone fiscal capacity and more private sector risk-sharing through a much bigger role for capital markets.

But the EU’s recent economic woes can’t be pinned entirely on the currency. After all, some eurozone countries—notably Germany—performed well during the crisis while some such as Ireland and Spain that were hit hardest are now among Europe’s fastest-growing. A country’s ability to withstand shocks is at least partly a reflection of the dynamism of the underlying economy and its potential growth rate. Countries that can reallocate resources efficiently from crisis-hit sectors and failing firms to those that offer good long-term prospects are likely to be able to sustain higher debt burdens.

The logic of EU membership is that countries have no choice but to make their labor and product markets more flexible, reduce bureaucracy, reform insolvency rules and speed up civil justice so that financially distressed but potentially viable firms can be swiftly restructured, and labor and capital reallocated. Governments can no longer trap resources so they must compete for them instead. Just as European companies were forced to overhaul their business models in response to European integration, countries are now being forced to do so too.

Inevitably, economic logic creates political challenges, reflected in rising support for far-left and anti-European parties across the continent. Indeed, that is why across Europe today—from Greece to Portugal to the U. K.—the major political fault line is no longer between traditional mainstream parties but between those who recognize the economic benefits of European integration in terms of greater dynamism and an emerging nationalist-socialist coalition that favors a return to an economic model based on national controls on the movement of goods, capital, services and labor.

Which side prevails may ultimately depend on whether voters in each country perceive European integration to create more long-term winners or losers. The BOE’s analysis suggests the economics at least are clear.