Never underestimate the capacity of Europe to tear apart our political parties and virtually destroy them. A referendum, or the vague offer of a referendum, is the favoured device of party leaders to avoid such self-destruction. It never works.

Here we go again. Until recently a near unity had descended on the Conservatives in relation to Europe. The Eurosceptics had won. The few pro-Europeans were silenced or had disappeared. Now, the Conservatives are split once more, this time between expedient Eurosceptics and more evangelical ones who have had enough and want to leave the EU.

The division is potentially lethal. In terms of the Coalition, Nick Clegg has already taken many blows and will suffer another humiliation if his plans to reform the Lords are scuppered. Clegg has told Cameron that he cannot go into the next election having failed to secure any of his key constitutional reforms while the Conservatives achieve all of theirs, adding that his MPs are fed up of voting through proposals that challenge all they had previously espoused. In such a gloomy context, the pro-European Clegg will not be thrilled at propping up a Conservative party preparing the ground for a referendum on withdrawal from Europe.

But the heightened danger is for the Conservative party itself. Is Cameron paving the way for an in/out referendum after the next election that will almost certainly divide his party before the poll and after it? No wonder he is so vague about what form a referendum would take. The stakes could not be higher.

The near-fatal schism in the Labour Party in the 1980s started with Europe. The SDP took embryonic form in the early 1970s when the pro-European Roy Jenkins rebelled against his party's whip and voted in favour of Britain joining the Common Market, as it was then. When Jenkins and others left Labour a few years later, Europe was a defining factor. The schism led to Labour being out of power for nearly two decades. In the 1990s, it was the Conservatives' turn to erupt over Europe. John Major's ministers got on fairly well with each other, but fell out over the Maastricht Treaty, illustrating that a split over a policy is much more poisonous than personal animosities.

The Conservatives will almost certainly go into the next election pledging a referendum on membership of the EU. I cannot see how Cameron can avoid it given the intensity of feeling in parts of his party. That means Labour will make a similar pledge. No leader could survive a campaign arguing he is not planning to "consult the people" over Europe when his main opponent is doing so, even if no one is acting out of a sudden passion for direct democracy. Referendums are offered only for reasons of party management or to avoid tough decisions during an election campaign. Almost unnoticed, Labour has indicated support for one of the Coalition's early revolutionary moves: legislation that triggers referendums on treaties that transfer any powers from the UK to the EU. George Osborne has suggested rightly that the significance of this paralysing innovation has not been recognised. This is not enough for those who seem to blame the EU for all our ills.

As a result, leaders who like to project a misleading Thatcher-like certainty in their public performances cannot do so over Europe. Instead, the much less fashionable Harold Wilson is their model. In the early 1970s, Wilson exclaimed to Barbara Castle that he was "sick of wading through shit to keep the Labour party united over Europe". He waded on, renegotiating Britain's terms of membership, or appearing to do so, and then staging a referendum in 1975.

It solved nothing. By 1983, Labour went into an election pledged to leave the EU without the need of a referendum. Labour's anti-Europeans no longer supported referendums once they had lost one. As for the issue itself, I hear no Euro-sceptic say now that a "binding" referendum was held in 1975 and we must all move on. Instead, they want another binding referendum, and if they lose it they will want another when they can win.

Cameron is in too weak a position to resist such calls. As a short- term ploy, a commitment to hold one might calm nerves, but only when he is more precise about timing and substance. He will then become even more Harold Wilson-like. I can hear his evasive words at the next election. "I cannot say how I would vote in such a referendum until we have renegotiated our terms of membership." But, unlike Wilson, Cameron won't be able to get away with a cosmetic renegotiation. Yet nor will he be able to secure substantial concessions from the EU either. Not for the first time, offering a referendum might get a leader through a difficult month or two, but will become an instrument of torture against him and his party before very long.

We will all be victims, too, as this contorted, over-the-top, energy-sapping, party-splitting furore is a foolish and irrelevant diversion from the urgent task of moving Britain and the eurozone away from the cliff's edge.

s.richards@independent.co.uk