When we opted last year to form a coalition with the Conservatives, the Liberal Democrats were not so naive as to think these elections would be anything better than extremely difficult. But last May we realised that none of the options that the electorate gave us were attractive.

Even if Labour had been united and willing to form a "coalition of the losers", the arithmetic did not stack up to anything like a stable majority without the Nationalists and the Democratic Unionists, which by definition would make such a coalition "not stable". A Tory minority government would have required the Liberal Democrats to abstain on votes of confidence, budgets and the Queen's speech, and we would have been accused – fairly – of propping up a Tory government while getting nothing in return. We would also have reneged on the clear commitment we gave that if we lost and there was a hung parliament, we would seek to provide the stable government that the country needed.

That left only the option of a Tory-Lib Dem coalition and it's simply unfair and irrational to criticise the party for voting overwhelmingly for a deal that secured, among other things: the return of civil liberties and the protection of the Human Rights Act from Tory attack, the prospect of constitutional reform including electoral reform, however modest, more funding for poorer pupils and early years, a fairer tax system (income tax cuts for the low paid funded by higher taxes on the rich) and significant steps towards a greener, sustainable economy.

That doesn't mean mistakes haven't been made in the first few months of the coalition, especially with the benefit of hindsight, or a "retrospectoscope" as we medics like to call it. The first of these was not to make more strongly the point that compromise is not betrayal; and assertion to the contrary by Labour, Green and even some erstwhile Lib Dem supporters does not make it so. Are European green parties betraying their principles when they form coalitions with larger non-green parties? It's funny how it's not "betrayal" when the Labour party ditched half their manifesto when forming Scottish and Welsh coalitions, or when Labour local council groups up and down the country make deals with other parties, including the Tories.

Second, there was the tuition fee disaster. The problem was not only that Liberal Democrats signed NUS pledge sheets (which were actually designed to lure Labour candidates away from their own party's pro-tuition fees, pro-Browne review policies) without finding a way of specifying more clearly the following health warning: "Voting against a tuition fee rise would apply to being in opposition and scrapping tuition fees could only be guaranteed by a majority Lib Dem government (ie, if there were 269 more Liberal Democrats had been elected)."*

Third, Nick Clegg and others were wrong to think that by excluding the tuition fee policy from the four priorities on the front of the manifesto, we could say that by securing those four top lines we were "delivering all our top priorities" if we got into power. The fact is that in the eyes of the media and the minds of the voters, opposition to tuition fees was a Liberal Democrat priority and it needed to be secured in the coalition negotiations, or failing that, at least the agreed mass abstention organised. While the failure has been mitigated by the progressive nature of the income-contingent loan repayment scheme, making what students owe more of a future tax code than a personal debt, it has since been "unmitigated" by the failure to predict and prevent so many universities pitching the fee level at £9,000.

Fourth, we should have acted much quicker to create mechanisms to help Liberal Democrat ministers identify and insist they prevent policy proposals outside of the coalition agreement, to which the Lib Dems were opposed, from being implemented. Parts of the free schools policy is a clear example and, of course, the NHS marketisation was another, although that one has been caught in time.

What we now need to do has already been set out by the party at its conference in March and we are working on it. Specifically the party has insisted that, from ministers downwards, we strive not only to identify that part of the government's record that stems from Liberal Democrat initiatives (the pupil premium, civil liberties measures, fairer taxes, etc) but also which part of the coalition government's record came from the Conservative party, which people should not assume we support as anything more than a coalition compromise. In addition, we have agreed again that ministers should be able to say in public what Tory proposals have been stopped or mitigated at the insistence of the Liberal Democrats – examples of this include the repeal of the Human Rights Act and excessive anti-immigration measures.

Finally, what we must not do is either panic or start infighting. I'm in touch with many grassroots activists, especially from the centre-left – the mainstream – of the party and there is rightly no wish to personalise against Clegg or any of his colleagues our disappointment at the election result. There is no new reason why the coalition will not go the full distance. As long as we learn from our mistakes, and improve our processes to block Tory plans that are not in the coalition agreement, there is no reason why we should not deliver what we agreed in the coalition programme and earn respect for so doing.

*The final sentence of the 5th paragraph was updated at 2pm on 7 May 2011