NICOLA Sturgeon has strongly defended SNP plans for Holyrood to have full tax and spending powers in the face of mounting attacks from Scottish Labour.

Writing in today's Sunday Herald, the First Minister says full fiscal autonomy is a "grown-up, responsible financial arrangement" and her opponents have chosen "the wrong battleground".

Her comments come as Labour concentrates its fire on full fiscal autonomy (FFA), which it perceives as the SNP's great weak spot going into the election.

Sturgeon argument was backed up by a new YouGov poll, which found overwhelming support for Scotland to have full powers short of independence, which implies FFA.

In Wednesday's BBC TV debate, Scottish Labour leader Jim Murphy pressed Sturgeon on whether SNP MPs elected on May 7 would vote for FFA - she said they would.

Labour seized on the comment and cited a recent report by the Institute of Fiscal Studies which said that, given the recent halving in oil price prices, Scotland would face an immediate deficit of £7.6bn under FFA, rising to £8bn by 2020, forcing it to borrow, cut services and/or raise taxes.

The SNP countered that if Holyrood had more powers and options under FFA, they could be used to grow the economy and so close the deficit gap.

But when Ed Miliband and shadow chancellor Ed Balls visited Edinburgh on Friday, Labour claimed Scottish GDP would need to grow at the near-impossible rate of 5.3% a year to close the deficit, and said the SNP would need to bring in austerity cuts worse than the Tories.

However, today Sturgeon says Labour and the other Unionist parties are simply trying to rerun scare stories of the kind used in the referendum.

They are "trotting out the same anti-independence arguments, but this time in the form of an assault on Scotland having the powers needed to grow our economy and build a fairer society," she writes.

"Strip away the clunky jargon, and FFA, as some have shortened it to, simply means Scotland being in charge of decisions on taxation, on welfare policies, on employment and on issues like the minimum wage - powers Labour, the Tories and LibDems don't want us to have.

"The Westminster parties seem to think it's a great time to trash this notion of grown-up, responsible financial arrangements for Scotland.

"Leaving aside the gigantic effrontery of any Westminster politician lecturing Scotland on fiscal rectitude when the UK's deficit is around £100bn and its accumulated national debt stands at more than £1.5 trillion, this tactic entirely misses the point.

"People across Scotland know and understand this is not a re-run of the referendum campaign. They want to hear about a different approach to the economy and a better, different vision to the dismal Westminster consensus on austerity."

She said the other parties had "made the potentially fatal mistake" of picking the wrong fight.

The new YouGov poll found overwhelming support for Scotland to have full powers short of independence, or FFA. Asked whether, if the SNP held the balance of power in a hung parliament, the country should ask for "greatly expanded devolution to Scotland, including all powers except defence and foreign policy" in return for supporting the government, 61% said Yes, 29% No, with 10% undecided.

However Sturgeon's confirmation that FFA means Scotland taking charge of welfare is at odds with a statement made on Friday by SNP chairman Derek McKay.

Asked on Sky News whether FFA meant the SNP was proposing to vote for opting out of the British welfare and pensions system, McKay replied: "No."

Murphy yesterday said FFA would mean "full fiscal austerity" and cut Scotland off from the pool of taxes raised across the UK.

Campaigning in Bellshill, he said: "The SNP's plans mean that extra investment in our NHS and our young people through fair UK-wide taxes would be turned back at the border.. with only Scottish taxes supporting Scottish public spending.

"Independent experts have said full fiscal autonomy would be facing a £7.6bn black hole in our finances. That would mean huge cuts to our schools and hospitals, or huge tax rises.

"Full fiscal autonomy would mean the end of the UK welfare state, the end of the shared UK pensions and the end of UK wide social security.

"We cannot let our poor, our sick and our vulnerable suffer five more years of austerity, imposed from the front door of Downing Street by a Tory Prime Minister, or through the back door with the SNP's reckless plans."

At soft play centre in East Kilbride yesterday, Sturgeon launched an SNP mini-manifesto for families promising SNP MPs would campaign for an £8.70 an hour minimum wage, higher child benefit and child tax credits, and stronger laws against maternity discrimination.

A copy of the manifesto will be delivered to all 2.4m Scottish homes this week.

Sturgeon will today step up efforts to woo Labour converts at an event in Paisley.

The SNP claims 400,000 former Labour supporters are "journeying" towards the party, based on polling data.

Meanwhile Scottish Labour said it was running its biggest ever election campaign, and planned to knock on 750,000 doors before May 7.

The Scottish Tories praised David Cameron's pledge of an extra £8bn a year for the English NHS, meaning £800m more for Holyrood through the Barnett Formula.

Deputy leader Jackson Carlaw said it was "a great opportunity for the Scottish NHS" and called on the SNP to spend all the money on health.

Former LibDem Scottish Secretary Michael Moore said only his party had a "fully-costed" plan to increase investment in Scotland's NHS by £800m a year.