SNP leader Alex Salmond has laid out his vision of a new partnership with England if Scotland gains independence.
Mr Salmond highlighted the positive relations Ireland has with the UK
In a speech in Falkirk, he set out how an independent Scotland would work with London and Dublin, on similar lines to the Scandinavian Nordic Council.
Jack McConnell this week set out his case for the union, saying devolution gave Scotland the best of both worlds.
Conservative leader Annabel Goldie said the country was at a "crossroads" and that independence was not the answer.
Mr Salmond's speech, to the annual conference of the Institute of Internal Auditors, highlighted the "positive and effective" relationship that the Republic of Ireland has with the UK.
He cited the British-Irish Council, which brings together the governments of Britain and Ireland plus the devolved administrations, as an example of close working relationships.
Mr Salmond said 800,000 Scots and 600,000 Irish people currently live in England.
"Irish independence didn't end these marks of our close and special historical relationship," he said.
"And if anyone in the modern Ireland of today were to suggest that a political union with London would offer them the 'best of both worlds' they would be laughed out of politics."
Mr Salmond also pointed to the experience of Scandinavian countries working together to promote common interests.
"Norway, Iceland, Denmark and Sweden have been in union with one or other for much of their modern history," he said.
"Like Scotland, England and Ireland, they have close ties of language, trade, family and friendship.
"But they made the positive choice to move to independence with real partnership at its core."
He said this was an example for Scotland and the British Isles.
In a speech on Wednesday, Ms Goldie said "a fresh approach to devolution" was needed.
"It's about using the Scottish Parliament to create the kind of Scotland which people thought they were going to get from devolution," she said.
"That will require a different political direction.
"I think that is an exciting opportunity and one which my party will grab with both hands."