THE cornerstone of the Coalition welfare reforms would be scrapped by the SNP under independence, giving Holyrood free rein to create a benefit system tailored to Scotland.

The Sunday Herald understands the Scottish Government's White Paper on independence will contain a pledge to abandon the controversial Universal Credit as part of plans for a more efficient and fairer welfare state.

The paper, which at 670 pages and 170,000 words is described by ministers as the most detailed blueprint of its kind ever published, also identifies March 24, 2016, as the day on which Scotland would once again be independent in the event of a Yes vote.

The date, the anniversary of the signing of the Act of Union which joined Scotland and England in 1707, will be officially announced when the paper is published in Glasgow on Tuesday.

Westminster sources said putting the date in stone was a blunder, as it would force the SNP to wrap up negotiations on leaving the UK, regardless of the deal it had achieved.

Deputy First Minister Nicola Sturgeon said the document would have "growth, jobs and fairness at its heart", with a promise of a "decent minimum wage" and support for greater participation by women in the workforce.

"Our message to the people of Scotland is simple: read it, compare it with any alternative future for Scotland and make up your own mind."

Promoted by Work and Pensions Secretary and Tory MP Iain Duncan Smith, Universal Credit (UC) is at the heart of the UK welfare reforms. It is intended to merge six working age benefits - Jobseeker's Allowance, employment support allowance, income support, housing benefit, working tax credit and child tax credit - into a single monthly benefit payment by 2017.

UC is meant to cut fraud and "make work pay" by ensuring low earners are rewarded for work, instead of seeing their earnings cancelled out by cuts to benefits and tax credits.

The Department for Work & Pensions estimates around 200,000 households in Scotland would be better off by an average of £25 a week, while 170,000 would be worse off by an average of £19 a week, although transitional arrangements should ensure no-one loses out if their circumstances stay exactly the same.

However, the policy has been plagued by delays and IT problems, with the Common Public Accounts Committee saying earlier this month that much of the £425 million spent on it so far may have to be written off due to poor management.

The commitment to drop UC if Scotland gains independence and takes control of welfare is contained in the policy section of the White Paper, effectively an SNP manifesto for the 2016 election if there is a Yes vote next September 18.

The pledge meshes with the SNP's pledge to abolish the so-called bedroom tax - the 14 to 25% cut in housing benefit for tenants deemed to have spare rooms.

A Scottish Government source said: "Scotland needs a welfare system that does not unfairly penalise people, and a better, fairer welfare system is a cornerstone of the fairness agenda which is at the heart of the White Paper."

Despite its bulk, the White Paper is intended to be a reader-friendly guide to independence, with a question and answer section on the economy, jobs, tax, pensions, broadcasting. defence, foreign affairs and welfare. There will also be two key policy sections.

First, what the current SNP administration would try to achieve during the 18-month transition period between a Yes vote and the pre-election dissolution of Parliament on March 23, 2016.

This is expected to cover key negotiations with the UK on issues such as national debt, a currency union, division of assets and Trident, as well as talks with international bodies such as the EU, UN and Nato.

The second set of policy choices covers what the SNP says it would do if elected as the first government of an independent Scotland in 2016.The pledges on Universal Credit and the bedroom tax appear in the latter section.

With an initial print run of 20,000 copies, the White Paper will also be available as an ebook, and in formats for Kindle, iPad and other tablets. There will also be printed and online summaries.

Sturgeon said: "This guide to an independent Scotland will be the most comprehensive and detailed blueprint of its kind ever published, not just for Scotland but for any prospective independent country.

"It is a landmark document which sets out the economic, social and democratic case for independence. It demonstrates Scotland's financial strengths and details how we will become independent [and] what a newly independent Scotland will look like.

"It illustrates how the powers of independence can be used to benefit individuals, families, communities and the nation as a whole. We want as many households in Scotland as possible to have a copy.

"The White Paper will now be the document that drives the independence debate."

The unionist parties were disparaging about the White Paper.

Scottish Conservative chief whip John Lamont said: "Considering the Scottish Government can't even establish the simplest of legislation in the space of 18 months, how on earth does it intend to create a separate state in that time?

"It seems like alcohol minimum pricing is years away from happening, and ministers have dragged their heels on a range of other subjects.

"No doubt this flimsy timescale is based on assertions and the goodwill of people and organisations the SNP hasn't even had the courtesy to approach."

A Scotland Office spokesman added: "Naming the date of independence ahead of a referendum result would only weaken the Scottish Government's negotiating position if Scotland voted to leave the UK.

"People in Scotland still don't know the full terms the Scottish Government would try to negotiate but the 28 members of the EU, Nato and the rest of the UK would all know that for the Scottish Government the date is more important than the deal."