Be careful what you wish for, you may receive it, runs the warning at the top of a horror story written by W W Jacobs more than a hundred years ago. For decades, the Liberal Democrats wished for an indecisive election that would deliver a hung Parliament in which they held the balance of power, rescuing their MPs from the spectre of eternal irrelevance.

But the grim reality of being a junior partner in a coalition is brought home by today's findings, from a poll of polls, which gives the Liberal Democrats only 11 per cent of the popular vote. It is their worst showing since the acrimonious end of the old Liberal-SDP Alliance 20 years ago. If there were a general election today, on these figures, the number of Lib Dem MPs would fall precipitously – from 57 to a mere 15.

At the same time, David Cameron is feeling the heat from the Conservative right, who accuse him of selling out too many of the party's core principles for the sake of holding the Coalition together. This creates the odd situation in the Oldham East and Saddleworth constituency, where the Conservative Party machine claims to be running a full-scale by-election campaign while their leader silently prays that the Tory candidate does not do well enough to humiliate the Lib Dems by pushing them into third place.

There are many pitfalls to coalitions, but that does not mean that we ask or expect that this coalition will be the last. Coalitions work well in other democracies, and in the UK we are going to have to learn to live with them. As a report this week from the Institute for Public Policy Research think-tank pointed out, there were 85 seats in the UK Parliament which neither the Conservatives nor Labour won in last year's election. This increasing tendency by voters to opt for one of the smaller parties suggests that we are in for a sequence of hung parliaments, even if the public votes no in the May referendum on voting reform. If they vote yes, we may never see another parliament in which any party has an outright majority.

There is ample evidence that public opinion is in favour of coalitions in the abstract, but they do not like all of what they see when faced with them in practice – the obvious example being Liberal Democrat MPs reneging on their election promise to oppose higher tuition fees for university students, an about-turn that has cost them so dearly in the opinion polls.

But horse-trading and the abandoning of manifesto pledges are a necessary consequence of hung parliaments, since no party has the voting strength to enforce its programme without negotiating with others. As the weaker party in the Coalition, the Lib Dems were inevitably going to be the ones making the more painful compromises.

But the Lib Dem leader Nick Clegg will have to do more than simply stand loyally in David Cameron's shadow while support for his party vanishes, which seems to have been his strategy to date. We are in an absurd situation in which leaders of both sides of the Coalition say that they are separate parties who will fight against one another at election time, but will not say openly what it is that they disagree about.

Lib Dem ministers would not have been caught out by undercover reporters last month uttering criticisms of the Tories in private if they had only had the nerve and honesty to say such things publicly. The Government would not collapse if the public occasionally listened in while Vince Cable and George Osborne sorted out their differences. A bit more openness would make for more transparent government, and might save the Liberal Democrats from implosion.