Leading article: Playing a risky game on Scottish independence

At first glance, the Prime Minister's efforts to seize the initiative on Scottish independence appear to be a clever piece of manoeuvring. On closer examination, however, they look worryingly like another instance of government by short-term tactics, of a desire for boldness that does not take account of the full spectrum of consequences.

The Government has certainly caused a storm with the proposal that Westminster "lend" the Holyrood Government the legal authority to hold a referendum that would be binding (as opposed to merely advisory), on condition that the vote take place within 18 months and that the question be just a straight Yes or No.

David Cameron says his aim is to lay to rest the uncertainty bedevilling the economy north of the border. The Scottish National Party claims the move is an unacceptable interference in Scotland's freedom to determine its future. It is also an irrelevance, the SNP says, because the political potency of a referendum would override any legal technicalities as to whether it was binding or not.

There is no question that it is in the interests of Alex Salmond – the SNP leader and Scotland's First Minister – to delay the referendum as long as possible. Mr Salmond is a formidable politician, and one who lacks neither guts nor guile. Were he confident of winning a referendum this week, then hold one he would. But, although opinion polls show support for independence creeping upwards, it is still only endorsed by around a third of voters.

Left to his own devices, Mr Salmond would likely leave the referendum until 2014. The longer he waits, the more time his formidable campaigning machine has to work, and the greater the likely unpopularity of the austerity-focused Tory-led Government. There is also the added bonus of coinciding with the 700th anniversary of Bannockburn.

But Mr Salmond's plans are not restricted to timing. It is the proposal to include a third option of "devolution max" in the referendum that is his masterstroke. Alongside options to stay within the UK, or leave it completely, Scots could be offered a half-way house of full fiscal autonomy but with political links to Westminster retained. "Devo max" might look like a contingency plan for Mr Salmond. But it is a mark of his political skill, shrewdly splitting the pro-union vote with a half-measure that can only tend towards full independence over time.

Is Mr Cameron's move an equally smart one, then? If the latest referendum proposals are agreed, they could both rule out "devo max" and force Mr Salmond to the polls sooner than he would like. So far, so strategic. But the Prime Minister has overlooked the risk he is running. The Conservative Party, never terribly successful in Scotland, is now so unpopular that it does not have a single MP. By couching the referendum deal in terms of "interference" from Westminster, the SNP hopes to make that unpopularity look like a lack of mandate. The very real danger is that Mr Cameron pushes wavering Scots towards the separatist arguments.

The swipe at Mr Salmond looks worryingly similar to Mr Cameron's ill-considered use of Britain's EU veto: an attention-grabbing move made without taking into account the full implications . The Government cannot avoid the politics of Scottish independence. If Mr Cameron wishes to preserve the union, he must focus not just on Mr Salmond but also on putting a stronger case in favour to the Scottish electorate.

So far, the SNP has made all the running, while pro-union arguments focus on the cost of a split without much mention of why Scotland might benefit from remaining within the union. The Prime Minister cannot rely on grand and risky gestures. He must put in some hard graft as well.