Former Labour Prime Minister has warned in a speech that it makes "no sense whatsoever" for Scotland to break its political links with England
Mr Brown instead tonight urged people north of the border to vote No in September's independence referendum to build a "stronger Scotland".
The former Labour leader made the plea as he gave his first speech as part of the cross-party Better Together campaign.
He told an audience at Glasgow University that when considering key issues such as the funding of pensions and the NHS, jobs in Scotland and interest rates, "it makes no sense whatsoever to break our links with England".
Mr Brown said: "This debate is about two visions of Scotland's future, about what best meets the needs and aspirations of the Scottish people.
"I am putting forward one vision of Scotland's future which is different from the Nationalists' vision that envisages a Scottish Parliament that breaks all links with the United Kingdom."
The former chancellor also blasted Scottish First Minister Alex Salmond's plans for an independent Scotland to keep the pound as part of a formal currency union with the rest of the UK, arguing this would leave Scotland in "a semi-colonial position" with no input or influence on the process of setting interest rates.
With Holyrood already due to get more powers and Labour and other parties proposing further devolution in the event of a No vote, Mr Brown set out a vision of a Scottish Parliament with increased powers as part of the United Kingdom.
"We are already a nation, we do not need a referendum to tell people that," he said
"The question that's got to be resolved is whether you want to break all political links with the rest of Britain, that's what it comes down to."
Mr Brown added: "I can see the virtue of an argument which says 'we're the Scottish National Party, London is to blame' but do you build the future of Scotland around saying 'we must abandon all political links with the rest of the United Kingdom', that is what the referendum question is.
"We are a nation, we have our national institutions, we have the Scottish Parliament, we're going to get more powers for the Scottish Parliament, the constitutional settlement will make possible better control over Scottish affairs, including tax raising powers for the Scottish Parliament,
"It makes no sense whatsoever to break our links with England."
On the crucial issue of currency in an independent Scotland, he insisted there was a distinct "Scottish reason" for not supporting the First Minister's plans.
"Mr Salmond wants to opt out of the United Kingdom, but he wants to opt in to the United Kingdom currency," Mr Brown said.
But he argued that while the Bank of England makes decisions such as the setting of interest rates, it is supervised by the UK Treasury and the UK Parliament in doing so.
Mr Brown said the Scottish Government wanted to "opt in to the currency, but not opt in to representation at Westminster and at the Treasury and the government that is going to supervise the Bank of England making these decisions".
He said: "It's impossible, it's not sustainable. The Scottish argument against Mr Salmond's proposals is he wants to opt in to the currency but opt out of the decision making processes we should be part of when deciding interest rates, mortgage rates and all the things that are the responsibility of the Bank of England, the Treasury and the United Kingdom Government.
"If you want to be part of this UK currency then you should be part of the decision-making process in the currency, therefore you have got to be part of the UK Parliament."
He insisted that meant the currency union being proposed was "not in Scotland's interests".
He claimed: "It would put us in a semi-colonial position where decisions are made about Scotland without any Scottish input into the decision making process. We have to have a right to make decisions that affect mortgages, the levels of business investment, that affect employment, inflation, the standard of living. It is a completely wrong position."