Britain appears to be almost inexorably set on a course that will see it cease to be a full member of the European Union. Today's Observer opinion poll, suggesting that, offered a choice in a straight in/out referendum, a two-to-one majority of Britons would be inclined to leave is but another indicator of the strength of anti-European feeling. It is now almost certain that both of Britain's principal political parties will feel obliged to offer such a referendum in their manifestos for the next parliament, triggered by the Tories' anxiety to defend their flank against Ukip and Labour's need to match them to appease the wave of Euroscepticism. Unless Europe suddenly becomes more attractive or pro-Europeans can make a stronger argument, the result of any referendum could look inevitable.

The only qualification to that assumption might come from either party in government being able to offer the referendum on a renegotiated relationship with more powers ceded to Britain. On that thin reed, dependent on the goodwill of European states who no longer trust Britain's interest in building Europe, hangs our European future. We will either be a semi-detached member – or not a member at all.

The likelihood of a complete exit will be brought one step nearer by this week's European summit, where 27 states are trying to agree the EU's budget for the next seven years. Agricultural spending used to account for the lion's share of European spending; now, the bulk of expenditure goes towards the infrastructure of poorer members, on research and development, and on the implementation of pan-European initiatives such as the proposed banking union. A freeze in spending, given the acute needs of southern and eastern Europe, is unlikely; probably the other 26 will settle on a small, real-terms increase.

Britain will not concur. David Cameron, locked between his own increasingly confident Tory backbench Eurosceptics and an opportunistic Labour party that has put tactical advantage before principle, knows that he cannot get such a deal through Parliament, nor can it survive the hysterical scrutiny of the overwhelmingly centre-right Eurosceptic media. He will be compelled to veto the deal, entrenching the distrust between Britain and its European neighbours, and making any concessions even to win a referendum on a semi-detached relationship much less likely.