Alistair Darling will today warn that independence will leave Scots with less power over their own destiny.
In a speech to the Foreign Press Association in London, the leader of the No campaign is expected to accuse the Scottish Government of exposing Scots to "turmoil, expense and risk".
"And for what? All in vain attempt to retain the things we already have," he will say.
Mr Darling's speech comes after Alex Salmond outlined his plans for an independent Scotland to foreign journalists.
The First Minister told them he would set up a written constitution which would guarantee Scots education and housing.
But Mr Darling will warn that independence carries dangers on the international stage.
He will say: "If we choose to exchange internal democracy for international diplomacy and economic co-operation for competition, we would be left dangerously exposed in foreign policy relations with our neighbours."
Yesterday the Coalition warned the "whole world order" could have to be renegotiated if two new states were created by independence.
Sources said an international crisis over nuclear weapons could be triggered.
The SNP denounced the claim, accusing UK ministers of thinking Scots were born yesterday.
The Coalition insists that post independence Scotland would be a new state, while the rest of the UK would be a continuing state. But the Scottish Government has disputed this.
A Coalition source said: "If the Scottish Government is right and our legal advice is wrong and two states emerge that have equal rights then you have an issue. Because one of the states that the world has agreed can have nuclear weapons has vanished."
He added: "If you have two new countries allowed to have a nuclear deterrent then you would have to renegotiate the whole world order".
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