The Tories have resurrected Project Fear and are spreading fake news about Scotland, Holyrood's Economy Secretary claimed
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."