There is a continuing and fascinating debate about the political wisdom of David Cameron and his team in entering so wholeheartedly into coalition with the Lib Dems after the inconclusive 2010 general election. Only time will tell if this was a masterful gamble that will transform the future of British politics and create a realignment enabling the Conservatives to regain their historical status as the natural party of government. Given the huge political prize of a stable Con-Lib coalition, it was arguably a small concession to offer the Lib Dems a referendum on the mildest possible form of change to the voting system — AV.

However, the British Constitution is of such fundamental importance that it is far from ideal to endanger it for the sake of an inter-party deal, no matter how attractive. A constitution should be stable and be altered only when there is a pressing reason for doing so and demand for change from a clear majority.

During the election campaign, a mere one per cent of the population — as measured by Ipsos MORI — rated constitutional reform as the most important issue facing the country. Since AV was merely one of a number of aspects of constitutional reform, it is reasonable to conclude that only a small proportion of this one per cent rated a change to this system as the key matter. There is no mandate for pushing a referendum on AV to the top of the political agenda.

If there is to be such a referendum, there is a strong argument for holding it only after the details have been worked out and approved by both houses of Parliament. Instead, at the Lib Dems' insistence, the date has been set for May 2011. This will leave no time to debate properly the many outstanding details about the wording of the referendum question and the rules for its administration and financing. The Lib Dems' motive for holding the referendum so early is clear from research by Dr Matt Qvortrup of Cranfield University showing that referendums are far more likely to win public approval if they are held during the honeymoon period shortly after a general election.

Leaving aside the legal problems about referendum funding left by the hastily-enacted Political Parties, Elections and Referendums Bill, 2000, and ignoring too the problem posed by the fact that the chair of the Electoral Commission is a former employee of a voting reform lobby, there is the matter of the wording of the referendum question itself. The coalition's political leaders have set out a form of words that asks the country to decide between the "Alternative Vote" and "First Past the Post". Yet the term "AV" itself is ambiguous. Under some forms, an elector is obliged to list all the candidates in a constituency in order of preference. Unless he or she does this, the ballot is invalid. Under other forms of AV, the voter needs to make only as many choices as desired. The two systems work very differently and raise separate questions of principle. Yet, the wording of the referendum question leaves open which form of AV is up for approval. Nor are these the only two forms of AV.