Nicola Sturgeon accused Labour of running a negative campaign

Nicola Sturgeon was responding to Tony Blair's comments that separation would be a huge financial risk and inject uncertainty north of the border.

She instead highlighted the success of independent countries such as Ireland, Norway and Iceland.

She added that the SNP was being backed by the "biggest voices" in business.

Ms Sturgeon pointed to the backing of former Royal Bank of Scotland chairman Sir George Mathewson, Stagecoach chief Brian Souter and Sir Tom Farmer.

Where there are issues when Scotland's voice needs to be heard, an SNP government will make sure that it is heard Nicola Sturgeon SNP deputy leader

Speaking to BBC Radio's Good Morning Scotland programme, she said: "These are serious business people and I think they know more about the Scottish economy than Tony Blair or Jack McConnell do.

"The biggest voices who have spoken in this campaign are the voices that are backing the SNP."

Speaking about the success of independent countries in Europe, Ms Sturgeon added: "They are doing exceptionally well because they have the power and ability to carve out economic strategies that suit their own national interest and that's the model that Scotland should be aspiring to."

She accused Labour of running a "relentlessly" negative campaign based on scare tactics and figures that did not add up.

"On Monday night, in a party election broadcast, this so-called black hole was �11.9bn," she said.

"By the [Labour] press conference on Tuesday morning it was �12.9bn - they are making it up as they go along."

'Democratic referendum'

She denied an SNP administration at Holyrood would have problems working with the UK Government.

"We will work constructively with the government in London in Scotland's best interests but where there are issues when Scotland's voice needs to be heard then an SNP government will make sure that it is heard."

Ms Sturgeon also denied the opinion poll gap between support for the SNP and support for independence showed the party was merely a recipient of protest votes.

Denying that independence was deliberately being put on the back burner, she said: "I don't think offering people a referendum within a four-year term is putting it on the back burner."

"All opinion polls show that regardless of people's views for or against independence, the vast majority of people right across party opinion think a democratic referendum is the right way to settle the question."

Ms Sturgeon also defended her party's plans to scrap Trident.

She said: "If you choose, as Labour wants to do, to invest up �100bn in new weapons of mass destruction, then there is an opportunity cost there as that is money than can't be invested in health, education, tackling crime, and better pensions.

"Politics and life is about choices, and we would opt not to invest in Trident but to invest instead in public services and the priorities of people across Scotland."

Meanwhile, on day three of official campaigning, the SNP focused on Trident, pensions, and the council tax and claimed the backing of "the biggest voices" in the business world.