Alex Salmond has called for the Lloyds TSB take over of Halifax Bank of Scotland to be frozen.
In his key-note speech closing the SNP's annual conference, he said the deal must be blocked while important questions were answered.
The first minister also accused Gordon Brown of contributing to the country's economic problems during his time as chancellor and prime minister.
He said the SNP were working to protect the economy.
Mr Salmond said that four weeks ago the Lloyds TSB takeover was the only game in town but circumstances had changed after the UK Government put forward money to help the banks.
Brown's Labour bust threatens to break records - and has almost broken our banking system
He reissued demands to know whether the money was dependent on the merger going ahead.
He said: "If the future of HBOS has indeed been secured then are we not entitled to ensure that any merger is in the public interest - that the public won't end up paying for the merger, paying for lost jobs and then paying for the restriction of competition.
"Until these questions are satisfactorily answered then there must be no merger.
"The Bank of Scotland has been around for 300 years. It is hard-wired into the social and economic fabric of Scotland. It does not deserve to be cast aside as a consequence of the age of irresponsibility."
Later in his address, the first minister attacked Gordon Brown's record on the economy.
Mr Salmond says the Bank of Scotland must not disappear
He told the conference: "Brown's Labour bust threatens to break records - and has almost broken our banking system.
"Under his watch our greatest company had to be rescued and saddled with 12% preference shares. And our oldest bank is threatened with disappearing as an independent force.
"And the prime minister thinks this is an advert for the Union?
"I would have thought that the condition of the economy, the fears of our people, the state of the financial sector, are a staggering condemnation of the state of the United Kingdom."
He highlighted that independent nations like Norway, Sweden, Denmark and Finland were among the few countries in Europe not heading towards recession.
Mr Salmond accused Gordon Brown of acting like he had not played any part in the UK economy going into decline, adding the prime minister had presided over an "age of irresponsibility."
He also accused Mr Brown of breaking down the barriers in the financial sector, presiding over the inflation of asset values and allowing the spivs and speculators to be totally unregulated.
He said: "Let the message ring out from this conference. Yes, we should have an end to the age of irresponsibility - not just in the financial sector but in the governance of the country.
"Sub prime? More like sub prime minister."
Mr Salmond said the prime minister had acted irresponsibly by proposing billions of pounds be spent on renewing nuclear weapons in Scotland and for keeping troops in Iraq.
He called for a new age of responsibility and a new time for Scotland.
He highlighted what the Scottish Government was doing to boost the economy - bringing forward building projects like houses, roads and schools.
Mr Salmond also said they had supported small businesses by slashing rates and that would continue.
"We are working to ensure our economy is best placed to weather the financial storm and well positioned for recovery," he said.
"And we are also working to protect the households of Scotland.
"We are the party of the home and the high street."
Mr Salmond announced the shared equity scheme for first time buyers would be extended so more young Scots could purchase a home.
The money available for the initiative will be increased from £24m to £60m and would be expanded to cover the whole country.
He concluded: "In this age of global uncertainty we know where the correct path for Scotland lies.
"Across Scotland we see a more confident nation - a nation that is ready to face any challenge.
"A nation whose destiny is independence.
"The new age of responsibility will usher in that new Scotland."
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