There is a deep and deliberate double deception at the heart of the Conservative position on Europe. David Cameron has been refusing for months to come clean on Europe – but he's about to be found out.

Such is the visceral anti-Europeanism in his party, ever since he became leader of the Tories he's had to keep on suggesting that he would hold a special referendum on the Lisbon treaty, even if it has been ratified and brought into force. But now the moment is virtually upon us, with the Czech Republic set to ratify it, Mr Cameron will have to come clean. I would bet my bottom dollar he won't guarantee a referendum on Lisbon.

Instead he will almost certainly unveil a heavily disguised fudge of a promise, with a guarantee that any future treaty that would cede powers away from the UK would be subject to a referendum. It'll be a remarkably hollow promise.

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After all, there are no plans anywhere in Europe to start drafting new European treaties. But Mr Cameron hopes he'll appease the Tory and UKIP right. He hopes people will blink and not spot the sleight of hand. I very much doubt he'll succeed, and his fudge will melt under heated sceptic scrutiny.

But the other deception Mr Cameron wants to get away with is his constant use of deliberately vague hints that sound tough but guarantee nothing. So he suggests they would renegotiate the treaty, but he must know this is impossible. Any treaty negotiation requires the unanimous agreement of all 27 governments – and every other government in Europe is absolutely clear they do not want another round of treaty talks. Indeed the one thing that unites every government and every political party in Europe (apart from the Tories) is that they do not want any more treaty negotiations and will do all in their power to block them.

Quite rightly they want to get on with the real issues that matter to European citizens – jobs, industry, competition with China and India, and tackling international crime. A Tory government determined to secure yet another new treaty would have to spend vast amounts of political capital needlessly trying to force the 26 other countries into doing a special new deal. What would they offer France, Spain, Germany, Poland and Italy?

There is an additional irony. Under the Lisbon treaty it is even more difficult to renegotiate the European treaties. The European Parliament now has a blocking power and can insist on a full-blown treaty convention, which would take years to complete. Since Mr Cameron has walked away from the mainstream in the European Parliament by abandoning the EPP grouping, he has next to no friends who would vote his way. So a renegotiation is a virtual impossibility and threatening it would simply set up a fruitless war with Europe that would be doomed to failure.

Mr Cameron also coyly intimates he would "repatriate powers to the UK", with a nod towards the social chapter. Again he flatters to deceive. Quite simply, the social chapter doesn't exist any more; elements like the right to paid leave and maternity pay are embedded parts of the single market now, scattered across several treaty clauses.

Any attempt to opt out of these provisions would rightly be seen by Paris and Berlin as an attempt to dismantle the common market and undermine the union. Leave aside the fact that I believe these measures are an important part of being a fair and competitive economy, the uncomfortable truth for Mr Cameron is that if he tried unilaterally to opt out, the European Court of Justice would immediately decide that the UK was in contravention of its treaty obligations. Mr Cameron would have set us on the path towards Britain leaving the EU, or being thrown out.

Already Tory isolation is damaging British influence. The Tories have abandoned the European People's Party group – the largest group in the European Parliament – and set up their own hand-picked group. The trouble is threefold. First, British businesses now have no direct access to the largest group in the Parliament. Second, the Conservatives are in a group of right-wing extremists with very dubious pasts, a matter which has already brought British conservatism into disrepute. And third, because a grouping has to have MEPs from seven countries and four of the countries represented in Mr Cameron's new group are solo figures from their country, the group would collapse if any one of them chose to leave. So Mr Cameron is completely in hock to the whimsy of four MEPs.

It is easy to point to the failings of the EU, but pursuing the British interest does not mean macho posturing. Our membership of the union is vital to our economic future. The single market has given British people the freedom to trade and work in the largest market in the world. That has meant three million extra jobs and annual exports of £370bn. Half the UK's inward investment comes from the EU, rising from £16bn to £106.5bn. British businesses don't want their futures put in peril by a reckless Tory policy of European wrangling. The head of the British Chambers of Commerce has said that Mr Cameron's policy "could do significant damage to British business interests". This is a warning that should not go unheeded.

We also have to ensure that the EU plays a far more effective role on the world stage. There are many global issues where a united EU voice added to ours will deliver real benefits to the UK. Last week the debate was about climate change, but I would add the Middle East peace process, Afghanistan and Pakistan, Russia and relations with the growing giants of India, China and Brazil.

But all of that requires a European Union that has actively decided not to spend its every waking hour arguing about the internal architecture of the treaties, but deliberately focusing on enhancing the prosperity and security of its citizens. In the end, that's the greatest Tory deception – to suggest that another bout of treaty negotiations would serve Britain or Europe well. The choice for Britain, and for Europe, is simple. Help the EU, with Britain at its heart, be a real leader on the world stage; or become spectators in a G2 world shaped by the US and China.

Chris Bryant is Europe minister