We are in the world of Lewis Carroll. Nothing is quite what it seems in the vote on a Europe referendum tonight. For a start it is only really about Europe and the Lisbon treaty for a minority of MPs (Bill Cash, David Heathcoat-Amory et al). For the party leaderships it is mainly about positioning, exploiting, or dodging an awkward issue.

Only a few can talk about principle with a straight face. As the invaluable Professor Philip Cowley, of the University of Nottingham, has pointed out, 72 Conservative MPs who are still in the Commons voted against a referendum in 1993 on the far more significant Maastricht treaty, and all but four are likely to vote for a referendum tonight. The Labour front bench was against a referendum then, as now, but 22 surviving backbenchers backed a ballot in 1993; most, but not all, will do so again tonight.

For David Cameron and William Hague, the vote has been mainly about trust in the Brown Government. All three main parties promised a referendum on the old constitution in their 2005 manifestos. If you look at what Tory leaders, and the “I want a referendum” campaign have said, it has virtually all been about MPs honouring this earlier election commitment rather than about the details of the treaty.

Labour and the Liberal Democrats argue that the Lisbon treaty is not the same as the constitution, not only in concept but also in key respects affecting Britain.

This puts most emphasis on the British opt-outs on home affairs and justice, which makes the treaty different from the one being ratified in the rest of Europe. This is a serious argument. But it has sounded slippery and what matters politically is appearance.

Hence, for Labour leaders, the priority is getting the treaty ratified as quickly as possible and then challenging the Conservatives to say whether they would accept it, or seek to renegotiate and scrap it (as many MPs and activists would like). This would lead to a crisis in Britain’s relations with the EU.

The Tory leadership has been evasive on what it would do.

The Liberal Democrats have, ironically, been in the most awkward position so far, caught by the conflict between their instinctive populism and belief in referendums and their traditional pro-Europeanism. Nick Clegg has a point that the underlying issue is less the treaty than Britain’s broader attitude to the EU. But he has found it hard to manoeuvre around the quagmire. The ejection of Ed Davey from the Commons and walkout by most Lib Dem MPs last week looked like a stunt.

The procedural debate yesterday about whether to permit an “in/out of the EU” amendment (heavily defeated) may have eased the internal tensions and allowed Mr Clegg to attack the two main parties. But he will be relieved if he can keep the number of Lib Dem dissenters from his abstention line down to single figures.

The Government should see off the demands for a referendum tonight. Approval looks straightforward, if probably lengthy, in the Lords. Several eminent Tory former Cabinet ministers will vote against a referendum, as will many leading Lib Dem peers. The real political test will come later, outside Westminster. Will voters regard the lack of a referendum as a breach of trust, as the Tories hope, or want to move on, as Labour hopes?

Treaty reforms

A full-time president for the European Council and a beefed-up foreign minister are the two big new jobs created in the EU reform treaty, referred to since December as the Lisbon treaty (David Charter writes from Brussels). Tony Blair has been suggested as a possible EU president by Nicolas Sarkozy, the French President, while other names mentioned as contenders include the EU’s two longest-serving prime ministers, Bertie Ahern, of Ireland, and Jean-Claude Juncker, of Luxembourg. The EU president would serve a two-and-a-half-year term and could only be reelected once; be responsible for coordinating meetings of the EU heads of state and representing the EU overseas; and would share the foreign responsibilities with the new EU high representative for foreign affairs and security policy, often referred to as the EU’s first foreign minister.

Other changes brought in by the Lisbon treaty include:

— Legal status for the Charter of Fundamental Rights (from which Britain has secured an opt-out);

— Legal personality for the European Union, giving it the power to sign treaties;

— Qualified majority voting (QMV), replacing national vetoes in 51 policy areas. Britain can opt in on judicial and police policy;

— Reducing the number of European commissioners from 27 to 18 after 2014;

— Changes in QMV voting weights from 2017 so that the support of 55 per cent of countries and 65 per cent of the population is needed to pass legislation, compared with 50 per cent and 62 per cent now. Blocking group must be at least four countries.

Times Recommends

• Deal struck to rescue Jodrell Bank
• S&M madam: Nazi claims are rubbish
• Operation Goodnight: holiday town curfew