Euroscepticism in Britain has been exacerbated by the eurozone crisis and a British exit from the European Union is now being openly discussed -- unless London\'s calls for reforms are taken seriously. Britain\'s ambivalence to the European project can be explained by a lingering conviction that the EU remains essentially a common market to facilitate trade, says Paul Whiteley, professor of politics at Essex University. \"Britain became a member because there were economic advantages. It was very much focused on trade,\" he told AFP. It is perhaps no coincidence then that British support for EU membership has dropped sharply in the last five years as the economic crisis has taken hold, Whiteley says. A regular opinion poll that he organises found in August that 61 percent of Britons wanted to leave the EU compared to just 39 percent who wanted to stay in. Philip Whyte, from the pro-EU think tank Centre for European Reform, agrees that the British \"never really signed up to the political dimension of the EU, the stuff about developing the foreign policy dimension or the single currency\". He traces a key reason for the growth in euroscepticism to the enlargement of the bloc towards eastern and central Europe in 2004. After an estimated one million new EU passport holders flooded into Britain in the space of a few years, \"EU membership was associated with the loss of control at the UK borders,\" said Whyte. Another reason was that \"the EU has been increasingly seen by the business community as the source of all sorts of unnecessary regulations\". Combined with the economic woes, those factors have hardened opposition to Europe within the ranks of Prime Minister David Cameron\'s Conservatives, which have led to clashes with their government coalition partners, the more EU-friendly Liberal Democrats. Margaret Thatcher, Conservative prime minister from 1979 to 1990, once famously opined that nothing good had ever come from Europe and Paul Whiteley notes that \"the EU has always been toxic for the Conservative party\". \"In the Conservative party now, it\'s not so much division between the eurosceptics and the \'eurosupporters\', it\'s between eurosceptics that want to stay in (the EU) and people that are eurosceptics to the extent that they want to leave,\" he said. The slip to the right has also been encouraged by the rise of the UK Independence Party (UKIP), whose sole interest is an \"amicable divorce\" with Europe. In that context of British hostility, few observers believe Cameron will receive a sympathetic ear from many of his fellow 26 EU leaders when he opposes any real-terms increase in the EU budget at a Brussels summit this week. Even less so when he tries in the months to come to secure exemptions for the City of London financial district, or for a repatriation of powers. Robin Niblett, from the respected foreign affairs think-tank Chatham House, said other EU states fear that giving in to British demands \"could open a Pandora\'s box of similar requests from other members\". Cameron\'s discomfort was heightened in October when Tory eurosceptics joined with their Labour counterparts in parliament to pass a motion urging the prime minister to insist on a cut in the EU\'s 2014-2020 budget. The prime minister says the best Britain can expect is a budget freeze in real terms -- but even that looks like a \'mission impossible\' when most members support an increase. Stephen Booth, research director at the eurosceptic Open Europe think tank, believes the current status quo is \"quite unsustainable\". \"A British exit is no longer a complete taboo. It is something that is a possibility if there is no new deal,\" said Booth. Philip Whyte believes an in-out referendum on British membership could be held around 2017, two years after the next general election. \"If a referendum was held tomorrow, it seems that the British would vote to leave,\" he said. Paul Whiteley, the Essex University professor, concurs that a British exit -- the term \"Brixit\" has already been coined -- is a possibility. \"But opinion can switch quickly,\" he cautions. \"If the eurozone crisis were to be rapidly resolved in a way to restore prosperity to Europe fairly quickly, you would see support for the EU membership coming back.\"