As the economic and political situation in Europe has worsened, public opinion in the UK has become increasingly Eurosceptic. Brits have traditionally been more ambivalent about their country’s membership of the EU than their Continental counterparts, and support for economic union and expansion of the Single Market has never been matched by support for the kind of political Union sought by France, Germany and others.

During the 1990s and early 2000s, when European enlargement and integration appeared to be delivering broad-based economic growth and prosperity, the UK’s relationship with the EU did not rank highly on voters’ lists of concerns. But the deepening malaise in the eurozone has exposed serious weaknesses within the EU, and has re-opened the debate about the value of continued UK membership under its current terms.

In an opinion poll carried out by YouGov in July 2012, 67% of respondents said they would favour holding a referendum on UK membership of the EU within the next few years and 48% stated that they would vote to leave, compared to just 31% who would vote to stay. Interestingly, when asked whether they thought that Britain would still be a member of the EU in 10 years, 63% of respondents said yes – irrespective of their own views on the question. This may simply reflect a belief that the current political leadership regardless of party has little interest in driving Britain towards a European exit.

However, David Cameron may not have the luxury of kicking this issue into the long grass. The political debate on Europe has also been reignited by the financial and Euro crises, and MPs from across the political spectrum are making the argument for a substantive renegotiation of the terms of the UK’s membership of the EU, if not for full withdrawal. But while the government is under serious pressure to hold a referendum as soon as possible, the timing of such a vote will determine everything. Cameron will have to start negotiations for a new British role within the EU very soon if he is to hold this referendum by the end of the current parliamentary term. This will not be easy, given the strain in British-European relations caused by his decision to veto an EU-wide treaty change last December.

If David Cameron is successful in renegotiating terms with Europe, there is evidence to suggest that Britain will vote to stay in the EU. Peter Kellner at YouGov explains that support amongst the British public for withdrawal significantly decreases if the Prime Minister succeeds in devising a new settlement with Europe, and then actively campaigns for Britain to remain a member on these new terms (42% would vote to remain a member while 34% would still vote to leave). While an optimistic signal for those who support EU membership, this outcome also relies on Europe’s willingness to compromise its terms with Britain. At the moment there’s no indication that they will do so.

Despite everything the public opinion polls indicate, there is one detail they currently cannot predict: the role of a more vocal case for Europe. IPPR has argued that while Eurosceptics have been making their argument since the European project began, pro-Europeans have been silent since the 1975 referendum – often only defending the status quo. A more constructive pro-European argument – from politicians, business leaders and the media – is greatly lacking from this debate. A British exit from Europe is not inevitable. But it certainly hinges on a more active pro-European argument being made to the British public.

Alex Glennie is a research fellow at the Institute for Public Policy Research (IPPR) and an author for Global Dashboard. Glenn Gottfried is also a research fellow at IPPR as well as an honorary research fellow at the University of Sheffield. a.glennie@ippr.org, g.gottfried@ippr.org