THE UK Government is to target a distinctive section of Scottish society in its battle to retain the Union, which could mean the difference between victory and defeat next September - the don't votes.

Alistair Carmichael, the Scottish Secretary, has revealed work is about to begin on persuading the significant minority, which could, if persuaded to take part, crucially swing the outcome of next year's poll one way or the other.

But the Yes camp insists it has a head-start, revealing it has for months been engaged in canvassing this particular group of the disenchanted and the dispossessed, using highly sophisticated means to get them to abandon what, in some cases, has become the habit of a lifetime, and vote.

One senior pro-independence source explained that traditional methods did not work with this group and that they had to be persuaded to take part in person and well before polling day. The SNP has engaged a "geographic and sectional approach" and is using local campaigners to sweep across Scotland to persuade them to make a difference in the Yes camp's favour.

"The picture is so different from the headline polls," the source claimed. "The No camp has a real problem with this group because these people are often marginalised, who feel they have nothing to gain from voting but the referendum is a big choice and it is their chance to make a real difference to Scotland's future."

In a snapshot in September, the don't knows accounted for 28% of the potential electorate. Many could in fact be don't votes. If the result were close, this group could be crucial

The Scottish Secretary said he recognised that Alex Salmond and the Nationalists were now heavily targeting the don't votes, seeking to persuade them that the referendum was a once-in-a-generation chance to change Scotland fundamentally.

"The Nationalists are trying to speak to that audience in ways that conventional political campaigning has never used in this country. We need to do the same," declared Mr Carmichael.

"The fact we know what we need to do is half-way to actually doing it. Once you start campaigning among people who don't normally vote, you are into territory politicians are not familiar with. We need to be very careful and very clever in the messages we engage when we are speaking to that audience," he added.

But Angus Robertson, the SNP leader at Westminster, who is co-ordinating the party's referendum campaign, stressed the SNP had been aware of the importance of the don't votes.

"Traditional non-voting groups are especially important in the referendum context. Not only is there a higher than average propensity among these to support the Yes campaign but with a higher turnout it's these voters who will help secure a Yes result," he said.