HOLYROOD'S opposition parties will get a say in formal cross-Border talks to shape an independent Scotland if voters opt to leave the UK, Nicola Sturgeon has said.

In a keynote speech on the constitution, she said Scotland's Labour, Conservative and Liberal Democrat leaders would argue the country's case as strongly as Alex Salmond if they were defeated in the referendum.

Opposition parties, trade unions, charities, churches and other civic bodies would also be consulted on creating a written constitution for the new state, the Deputy First Minister said.

In a bid to reach beyond SNP supporters, she said: "Although the independence negotiations that will follow a Yes vote will be led by the Scottish Government, we will not act alone.

"If there is a Yes vote for independence, then let me make it clear – the Scottish Government will invite representatives of the other political parties and of civic Scotland to contribute to those negotiations.

She added: "When the people have spoken, we will emerge from it as one united nation.

"We will be team Scotland, and at that moment in our history, I am sure – whatever they say this side of the referendum – that Johann Lamont, Ruth Davidson and Willie Rennie will argue Scotland's case as strongly as Alex Salmond and Patrick Harvie."

Under the SNP's blueprint for independence, a Yes vote would be followed by 18 months of intense negotiation with the UK Government to thrash out details of the split before the next Holyrood election in May 2016. UK and Scottish Ministers would have to agree Scotland's share of the national debt and strike deals on the armed forces, the BBC and other shared institutions.

The offer to opposition parties of a "very real" say in shaping an independent Scotland came in a speech pitched squarely at broadening the appeal of independence to non-SNP voters.

Ms Sturgeon said the late former First Minister Donald Dewar's Scotland Act, which gave birth to the Scottish Parliament and took Scotland "half way" to independence, was "one of the finest pieces of legislation ever".

Her reasoning for independence, she said, was not based on Scottish identity but to ensure the country could choose how it was governed, stressing her own commitment to social justice.

She said she did not believe independence was essential to preserve the Scottish identity.

But, she said: "I don't agree at all that feeling British – with all of the shared social, family and cultural heritage that makes up such an identity – is in any way inconsistent with a pragmatic, utilitarian support for political independence.

"My conviction that Scotland should be independent stems from the principles, not of identity or nationality, but of democracy and social justice."

Her speech to business leaders, academics and representatives of civic Scotland at Glasgow's Barony Hall attracted fewer than 100 people.

Patricia Ferguson, Scottish Labour's constitutional spokesperson, said: "All parties and beyond will need to come together after the referendum and unite behind the result so that we can work together for a better future for Scotland. I only hope she is just as quick to accept the result should the people of Scotland vote to stay in the UK."

Scottish Liberal Democrat leader Willie Rennie MSP said if there was a Yes vote, "we would work together and we would make the best out of a bad situation." He added: "I would hope that Nicola Sturgeon and the SNP will accept my invite and work with us to secure a federal United Kingdom in the event of a vote to stay in the UK in 2014."