Keith Brown hit out at the Conservatives as the Westminster Government clashed with Nicola Sturgeon’s SNP administration over the prospect of a second independence referendum.
But Mr Brown said if the UK Government refused to sanction such a vote it would be a democratic outrage.
SNP ministers insist they have a “cast iron mandate” to hold another ballot after the 2016 Holyrood manifesto indicated this could take place if there was a “material change in circumstances” from the 2014 vote - such as Scotland being removed from the European Union (EU) against its wishes.
Mr Brown said: “If the Prime Minister refuses to engage on the terms of a referendum before the UK leaves the EU then she is single-handedly blocking the people of Scotland having a choice over their future.
“That would be a democratic outrage.”
He added: “The status quo is no longer an option. We now face a hard Brexit from a hard right Tory Government, and all the damage that will cause to jobs and the economy of Scotland.”
The Economy Secretary went on to tell the SNP spring conference in Aberdeen that an independent Scotland would continue to trade with the rest of the UK.
Scottish Government figures published at the start of 2017 showed sales from Scotland to the rest of the UK are worth four times the amount of sales to other countries in the EU.
But Mr Brown said: “It may come as a surprise to some people but trading with your nearest neighbour is the norm the world over, but the inconvenient fact for our opponents is that these countries who trade with their neighbours are in fact independent countries.
“Canada’s biggest trading partner is unsurprisingly the USA, with more than 75% of their exports going to the United States.
“Are our opponents really saying that Canada cannot be independent because their largest trading partner is America?
“Of course not, because their argument is illogical nonsense.
“As Theresa May and Boris Johnson run round the world desperate to strike a trade deal with anyone and everyone, we are supposed to believe that they will trade with every other country, but not an independent Scotland.”
He hit out at the Tories and other Unionist parties, saying: “They’ve been spreading fake news for years about our economy, our resources and the kind of future that we could build if Scotland chose an independent future.
“Talking Scotland down is their stock in trade.”
And he said Project Fear - the nickname given to the Better Together campaign to keep Scotland in the UK in the run up to the 2014 independence referendum - was “back in spades”.
Mr Brown told the conference pro-UK politicians “have so tied themselves in knots with their absurd proposition that they are saying Scotland in the single market can’t trade with the UK, which can only mean that the UK won’t trade with any other member of the single market.”
He added: “We know it’s rubbish and so do they. But it shows us that Project Fear is back and back in spades.”
Meanwhile, Holyrood Health Secretary Shona Robison insisted Scots have the right to choose independence as an alternative to Brexit, as she warned quitting the European Union would threaten the future of the NHS.
A hard Brexit, taking the UK out of the single market, would put the future of Europeans working in the NHS in doubt, and would mean “greater Tory cuts” to Scotland’s budget, Ms Robison said.
She called on her English counterpart Jeremy Hunt and Prime Minister Theresa May to “get on with the day job” instead of “pursuing their hard-right Brexit agenda”.
While SNP ministers have been accused of ignoring day-to-day issues such as health and education as a result of their “obsession” with independence, Ms Robison levelled the same charge against the Tories at Westminster.
She stressed the key role EU workers play in the NHS, with European citizens accounting for one in 20 doctors.
She said that one medic, who had spent more than 25 years working for the health service in Scotland, had been left feeling he “was no more than a pawn in Theresa May’s Brexit game”.
Ms Robison said: “Scotland must have the opportunity to protect these European nationals - our friends, neighbours and families - and have the ability to attract their successors in years to come.
“Let’s send a clear message today to the staff in our NHS and care services from EU countries, and those from other parts of the UK and further afield - Scotland is your home and we will do everything we can to ensure your future.
“Frankly, rather than pursuing their hard-right Brexit agenda, it’s time that Theresa May and Jeremy Hunt got on with the day job.
“Between the prospect of a hard Brexit hitting staffing and tuition fees saddling nurses and midwives with huge debts, you have to wonder just what Jeremy Hunt’s long-term plan for the NHS in England actually is, if he has one at all.”
The Tories’ “folly” of an EU referendum has placed Scotland - which voted to stay in the European Union - at a crossroads, Ms Robison said.
“One road leads to a hard Brexit, where the future of our EU staff are threatened and with it the very fabric of our NHS, and there is a clear path towards yet greater Tory cuts to Scotland.
“The other road offers us choice - the ability to choose a different future for our country.
“I choose independence, I choose the road where we can protect our European staff, deliver our vision for the future and ensure the future of an NHS that is publicly owned, publicly run and free at the point of use.”
Ms Robison said this “is a choice that is our right to make” and told SNP activists: “It’s a choice that we can and will deliver.”