The battle for Scotland's future, and the future of the United Kingdom, finally began last week with the intervention of the Prime Minister, David Cameron, over the timing of an independence referendum.

It is too early to tell who has won these early skirmishes. However, it was unwise for the leader of a party which has scant representation in Scotland – the Conservative Party – to appear to dictate the timing and the conduct of a decision that must be taken in Scotland by Scots alone.

By the same token, it was unhelpful for the First Minister of Scotland, Alex Salmond, to tell the Prime Minister to "butt out" of the debate about independence. Of course, Cameron has a right and a duty to be involved in the decision-making process, even if the final decision is for the Scottish voters alone to make. It is in everyone's interest for this matter to be resolved at the ballot box rather than in the courts, and it is perfectly reasonable for Westminster to delegate to Holyrood the right to hold a legally binding referendum rather than merely an advisory one.

However, any attempt by Cameron and Westminster to attach strings to this arrangement will only be counter-productive for those who want to keep the UK intact.

The SNP Government has finally set the date for the referendum – autumn 2014 – and this is a reasonable time scale for such a complex matter to be consulted upon and debated. Rushing to a judgment on independence would surely be a mistake, and would have been attacked by the very unionist parties who now say the First Minister is delaying the ballot to gain political advantage.

There is a good argument that the UK Electoral Commission should have some involvement in the referendum, although in an advisory capacity, if only to ensure that there is confidence in the result across the rest of the kingdom.

If there are reservations about the independence of the commission, they should be resolved in the coming consultation period. Similarly, everyone who is registered and eligible to vote in Scotland should be allowed to vote in the referendum. There is a case to be made for allowing 16-year-olds to vote in the referendum, and indeed in elections, but that should not be a deal-breaker in these negotiations.

The big question is the question itself. The danger of having several options on the ballot paper is that there would be scope for argument over which one is to take precedence. If a majority of Scots vote for independence, but a larger majority vote for another form of devolution, which result takes precedence? Also, while there is clarity on the meaning of independence, there is as yet no settled definition of what is called "devolution max", or federalism.

Rather than present a number of contradictory options, the referendum ballot paper should ask a single straightforward question along the lines of: "Do you wish Scotland to leave the United Kingdom and become an independent sovereign state. Yes or No." The shorter the better, to allow minimum scope for lawyers to pick the meaning apart as lawyers are trained to do. This is the question that the SNP has always said is its preferred option, and it should stick to that.

We recognise, however, that this might leave many Scots who support neither full independence, nor the status quo, feeling disenfranchised – those who wish Holyrood to gain power over all laws, taxes and duties with the exception perhaps of defence, foreign affairs, monetary policy and the currency. This option should certainly be fully explored, if only because the opinion polls indicate that the vast majority of Scots currently wish to see the Scottish Parliament given greater powers within the UK.

Over the next two years, it will be up to the opposition parties in Scotland and to Scottish civil society groups to fashion this into a coherent proposal. This could then be put to the people of Scotland in a separate ballot after a "cooling off" period. No-one should restrict Scotland's freedom to choose, but the choices offered must be clear and unambiguous.