Alan Trench: We need ceasefire in Scots cold war

As an independence referendum's wording takes shape, the standoff between the two sides in the debate has to end

A PLANNED referendum would allow the public to vote on two proposals: one would give extra powers to Holyrood, short of independence, while the other would enable independence

The debate about a referendum on Scottish independence has become even more heated since the May election. The First Minister does not want London to "meddle" in the holding of a referendum. The UK Scottish Secretary supports two referendums, "personally". The Prime Minister does not and insists there should only be one. This macho shouting match takes place against a backdrop of what is almost a constitutional cold war. Since 2007, two constitutional processes - the SNP-led "National Conversation" and the unionist parties' Calman Commission - have been under way, but scarcely linked to each other. The prospect of a referendum means that is no longer tenable.

There are some good reasons to prefer having two referendums. It enables the Scottish Parliament to initiate the process, but the limits on Holyrood's powers mean it can't go so far as to endorse independence. A second referendum also means that the final "determinative" vote takes place after negotiations, when it will be clearer what sort of country an independent Scotland would be. A great deal will depend on some difficult issues - the shares of UK debts and assets, including the North Sea oil and gas reserves, or the terms of EU membership - which will only become clear through those negotiations.

Having two referendums has disadvantages. It will extend uncertainty, with possible effects on the financial markets. SNP supporters may fear that it creates an unnecessary obstacle to independence, while many in the unionist parties are afraid it will encourage people to vote Yes the first time, but No at the second poll when it will "really" count. But it has been endorsed by some surprising figures, including (in a Canadian context) by the former Quebec premier and founder of the sovereigntist Bloc Qubcois, Lucien Bouchard.

The SNP gained a powerful mandate at May's elections. But it was the support of about 45 per cent of the electorate, on a turnout of 50 per cent. In other words, fewer than a quarter of Scottish voters actually voted for the SNP, and many of them voted for it despite the party's commitment to independence, not because of it. There is also clearly support from a majority of Scottish voters (not just those who voted SNP) for a more extensive form of devolution than the current Scotland Bill offers, and to have a say on Scotland's future through a referendum. There are various constitutional mechanisms to deliver that, but they will only work if both London and Edinburgh can agree some ground rules for the conduct of the debate - something they have failed to do so far.

The "two referendums" approach is the easiest way of finding a route to independence through the existing constitutional framework. It helps overcome the SNP's fundamental problem - that the referendum they want is one that Holyrood has no power to call. It's not necessarily the only way to consider independence, but other approaches mean changing the existing framework. For that to happen, though, there have to be other changes as well.

First, the constitutional cold war has to end. It's not enough for each side to divide the constitutional debate into their own parts and then refuse to allow the other side onto it. This is much more an issue for the unionist parties than the SNP - while the Scottish Government submitted evidence to the Calman Commission and invited all views to be included in the National Conversation, the unionist parties refused to allow the Calman Commission to consider independence and failed to address arguments for it seriously until the Scotland Bill committee sat during the last parliament. What's now needed is a process that puts all the options as clearly as possible before the Scottish people. Unionists and nationalists must be willing to debate with each other about their visions for Scotland.

Second, there needs to be greater clarity about what sort of country an independent Scotland might be. The SNP needs to set out its plans more clearly, and voters need to know what the UK government thinks of those plans, and how it sees relations between an independent Scotland and the rest of the UK. It's not necessary to dot every "i", but for a referendum to be held before negotiations, both sides need to spell out where they stand and voters must be able to understand how realistic those aspirations are. In effect, there should be some "pre-negotiations". Otherwise, voters are being asked to vote on an SNP wish-list, not a real proposition.

Third, the formal process has to match the political reality. The Scottish Parliament simply does not have the power to ask a referendum question that would directly lead to independence. However, if there is basic agreement between London and Edinburgh, it is quite easy to confer the powers on it to do that. There is a very suitable mechanism in section 30 of the Scotland Act 1998, which requires orders altering the scope of "reserved matters" to be approved by both houses of parliament at Westminster and the Scottish Parliament.A section 30 order could give Holyrood the power to call a referendum on a "real" question, not a "Should there be independence negotiations?" one. This could also be used to ensure that the question is a clear and impartial one, and perhaps provide for the regulation of the referendum. The Scottish Government proposed an ad hoc commission with no role in reviewing the question. The Electoral Commission would have no role, and Westminster legislation would be needed to give it one. But the Electoral Commission did not come well out of either the AV referendum or the March one on legislative powers in Wales.

Deciding those ground rules also means deciding how many questions there would be. It may be a bitter pill for the SNP to swallow, but a single referendum should not put three options before the voters. The referendum must produce a clear outcome, and a multi-option or multi-question "preferendum" would be very unlikely to yield a majority for any option, least of all independence. Even if one option has a clear lead, that will not be enough to ensure that there's wide acceptance (in England and other parts of the UK, as well as by unionists in Scotland) that the Scottish people have chosen independence. The effect of a referendum is not just to establish what the public think, but to demonstrate it. A mandate from a multiple-choice referendum may be a powerful tool for negotiations with the UK government, but it could not be the basis for an independent state. A multiple-choice referendum is really implicit acceptance of the need for two referendums.

All this means calling a halt to much of the party-political tactical manoeuvring that has gone on. While the unionist parties have on the whole been somewhat worse at this than the SNP, the Nationalists are far from blameless either. Campaigns by Alex Salmond to attack any questioning of the Scottish Parliament's right to hold a referendum do not help, nor do attempts to undermine the standing of the UK Supreme Court if it has to adjudicate on the lawfulness of a referendum bill.

This sort of constitutional politics comes awkwardly to British politicians, and it needs careful choreography and a delicacy of touch. At the moment, it's more like watching elephants trying to dance.

Perhaps it's time to recognise that what the wider public audience needs is different to what they've been getting so far. After the punk-rock pogoing, now it's time for some ballet lessons.

• Alan Trench is an honorary senior research fellow at the Constitution Unit.