Garvan Walshe was national and international security policy adviser to the Conservative Party until 2008.

Fragging is not an obscure form of abuse once practiced at the finer public schools. Nor is it a faux-genteel obscenity (call to your mind someone who exclaims “sugar!” when the children are around). It comes from the Vietnam war and means to be hit by a “fragmentation grenade” – an unpleasant weapon that explodes after being thrown, releasing fragments of shrapnel to lacerate the flesh of its victims.

The results of elections in Spain and Ireland show parliaments hit by such a grenade. After Trump’s performance in Michigan, the Republican Party is well and truly fragged. This time the Democrats have escaped thanks to the strength and efficiency of the Clinton machine. Our own Labour party hasn’t been so lucky.

Formal coalition doesn’t help: Horst Seehofer of the Bavaria-based CSU has been making every effort to undermine his sister party’s leader over refugees.

At least the fact that voters see the Conservative party as divided isn’t hurting us in the polls, because the EU referendum provides us with a way to confine those divisions to an issue on which voters will have the final say.

But first activists, and now, as the fissiparous assemblies convening in Dublin and Madrid show, voters have forgotten the central purpose of political parties: they do not exist to give life to specific ideas and preferences but aspire to be coalitions capable of exercising power.

Voting is not, and cannot ever be, a matter of consumer choice. The unique genius of the free market lies in the quantity and diversity of products it supplies. Each of us gets what we want to pay for and isn’t, in normal times, lumped with the consequences of someone else’s preference. We live our private lives à la carte, and are much happier for it.

Politics is more like one of those old-fashioned Italian dinners where everybody is expected to have the same thing. If people vote for the pork, that’s what we’re all getting, even those of us who preferred beef or vegetables. It is usually easy enough to make a tolerable choice when we’re just ordering one dish. But it becomes frightfully impossible when people have different preferences for starters, side dishes and pudding.

Politics is a collective business. Even when governments elect to allow experimentation in some areas by decentralising schools or health care, an awful lot of governing – foreign affairs, national defence, immigration control, taxation, law and order – still can’t be run à la carte.

This would not be so much of a problem were it not for the success of a seductive French doctrine: that the government is legitimate only when it represents, in some way, the views and opinions of the people. It’s a fine ideal, but ignores the obvious fact that the people don’t only disagree (when two well-organised camps alternate power against a background of stable institutions, things work quite well), but they don’t even form organised social classes pursuing their conflict through the political system.

Worse, the fragmentation has no single cause.

In Spain, there is no stable left- or right-wing government that can be formed. The far-left Podemos are toxic to the other main political parties, while the outgoing Partido Popular Prime Minister Mariano Rajoy has converted himself into a symbol of his party’s intransigence by gambling that the others would eventually do a deal with him rather than risk new elections. It is a gamble that looks like it will have failed. In Ireland, differences of political culture between Fine Gael and Fianna Fail make it almost impossible to have a grand coalition, while the Irish left is too divided to even resemble an organised force. Sinn Fein had thought to establish itself as leader of the anti-austerity left, but its support is limited by its history as the political wing of the IRA. In the United States, both parties are in trouble because their activists have given priority to finding a candidate who expresses their emotions over one who stands a chance of implementing at least some of the policies they claim to agree with.

And though Britain’s first-past-the-post electoral system limits the effects of fragmentation, both UKIP and Labour conducted their campaigns as if the coalition parties did not between them command both a majority of votes in the country and seats in the House of Commons.

Yet, it is in parliaments that the answer to fragmentation is to be found. What Spain, Ireland and Britain share has been a notionally parliamentary government where the executive is in fact in almost complete control. But a fragmented parliament won’t support such an all-powerful government. What is needed is much closer to the eighteenth century idea of an “administration”: in charge of government departments, but which in exchange for having conceded such charge, returns considerable legislative power to shifting majorities of the parliament.

This would allow stable government to continue in Ireland and Spain. Whether voters will tolerate this amount of open political horse-trading is another matter.