SNP hard-liners angered by the absence of the independence option in the devolution referendum were urged yesterday not to risk undermining a double-Yes vote by recording that protest on the ballot paper.

The party's 300-strong national council meeting in Perth at the weekend voted overwhelmingly to lend its weight to the Yes-Yes campaign, in the face of a small but voluble opposition led by former leader Gordon Wilson, and yesterday it was announced that three of the SNP's senior figures, each with a reputation for expertise in the streets and on the doorsteps, would be taking up seats on the executive of Scotland Forward.

Policy vice-convener Alex Neil is joined by former MP George Reid, and Monklands East by-election candidate Kay Ullrich - the latter two being SNP executive members covering the respective remits of industry, technology and employment, and health and social policy.

The presence of such high-profile appointees to the executive was welcome by Scotland Forward but also seized on by opponents as showing the contradiction at the heart of the Yes-Yes campaign - that, while Labour argue that their devolution scheme offers the best hope of modernising and thus saving the Union, their new allies in the campaign see Home Rule as a base-camp on the way to the eventual summit of independence, as SNP president Winnie Ewing put it during Saturday's debate.

It emerged in the debate that some traditionalists who distrust devolution as a potential block on independence were minded to fill in the two affirmative boxes in the ballot but then add an additional word or comment, making clear their main preference. It was claimed by Gordon Murray, of Cumbernauld, speaking as a former returning officer, that provided the voting intentions were clear, this would not result in a paper's being declared spoiled.

However, there was a strong warning from both SNP leader Alex Salmond and from Bill Spiers of Scotland FORward against risking this, as there was every chance that this would invalidate the ballot paper. ''If you start scrawling something on the ballot paper you are putting yourselves in the hands of the returning officers,'' said Mr Salmond, while Mr Spiers said: ''It has to be spelled out quite clearly: if you write anything across your ballot paper it will be a spoiled paper.''

The amendment calling for the SNP not to link up with Scotland FORward and to permit a conscience clause for those who distrusted devolution was moved by Christine Creech and supported by, among others, Mr Wilson, who made an impassioned plea for Nationalists not to get bogged down in the swamp supporting something that was Labour's policy, not theirs.

But Mr Salmond claimed: ''If Scotland dumps the opportunity to have limited self-government, I think it will throw the country into a democratic dark age and a mood of depression, the like of which we have never seen before.''

Only a handful voted in favour of the amendment, and the resolution to play a vigorous part in the campaign was passed almost unanimously.

Scottish Secretary Donald Dewar responded: ''I am absolutely delighted by their support. The more the merrier.''

However, Scottish Tory chairman Raymond Robertson wrote yesterday to Mr Salmond, asking whether the SNP was now effectively giving up on its goal of breaking up the UK and creating a separate Scottish state. ''Or do you support the creation of a tax-raising Scottish parliament because, like me, you see it as the fastest means of destroying the Union?''

Mr Salmond replied that Commons exchanges had made things clear. ''Both Donald Dewar and I have agreed that the future direction of Scotland is a matter which can only be decided by the judgment of the Scottish people.

''Given that the Tory party in Scotland have no MPs, then I can understand if you have failed to follow these debates in Hansard.''