Editorial: Cameron gives the game away

This newspaper has been, since its foundation in 1990, a supporter of Britain's membership of the European Community, which became the European Union three years later. We recognise, however, that this is a position that has been undermined by many of its supporters. For too long, it has been held to be self-evident that EU membership is a good thing, and anyone who disagreed was derided. Yet it is not self-evident to most of the British people who, since the euro went critical in 2010, have told pollsters that they want the UK to leave.

It is worth returning to the basic arguments for and against British membership of the EU, therefore. The Independent on Sunday welcomes David Cameron's decision to do just that, by delivering a speech in the Netherlands next Tuesday. But the speech that has become so loaded with significance that Daniel Day-Lewis would be unable to do it justice on a Hollywood set littered with bodies.

We did not expect the Prime Minister to try to repeat Harold Wilson's scheme for holding together his disunited party, without any of the old schemer's guile and charm. Mr Wilson engaged in a cosmetic renegotiation of the UK's terms of accession – something to do with New Zealand butter – so that he could claim to have secured a better deal to put to the people in the referendum.

Mr Cameron seems determined to repeat history as both farce and tragedy. Farce, because he gave away his negotiating position by saying in July that pulling out of the EU would be "a complete denial of our national interests". (George Osborne, the Chancellor, seems to have belatedly spotted the flaw in this plan, saying last week: "In order that we can remain in the European Union, the EU must change.") The Prime Minister's policy is also tragic, in that he and the Chancellor seem to have been buffeted into promising a referendum that could, as in Wilson's case, result in the confirmation of Britain's membership, but which could mean the ending of it. A referendum at some point is probably necessary and democratic, but promising it now risks several years of business uncertainty, as Ed Miliband warned last week.

The EU is some years away from completing the closer political union of the eurozone; still further from agreeing the relationship between the euro and non-euro members of the single market. Any British prime minister ought to fight for the national interest in those negotiations ahead, and then and only then seek the consent of the British people for any new arrangements. By trying to buy off the Ukip threat on his right flank, Mr Cameron has succeeded only in encouraging the notion that withdrawal would end all our irritations with Europe. Party interest has triumphed over national interest.

The trouble is that the worst people to make the case for the EU are those who told us adopting the euro was a good idea. Lord Heseltine, you are not helping.

The case for Britain in the EU, to go back to the beginning, is that the single market makes us richer, and that we could not be sure that we would have access to it if we left. Mr Cameron had a historic opportunity to be the Eurosceptic voice that would make that argument. Instead, the only message from his speech next week will be whether and how he promises an "in or out" referendum.

We hope we are wrong, but it looks as if the way the Prime Minister has gone about next week's speech has been "a complete denial of our national interests".