Nicola Sturgeon has accused Boris Johnson of "democracy denial" and warned his rejection of a second referendum makes independence "more certain."
The SNP leader slammed the Scotland's looming departure from the EU at the end of the month, as she raised fears over a "race to the bottom" on key social areas at First Ministers Questions today.
"I believe that we could have so much better if we were an independent country able to co-operate in the European Union in our own right," Ms Sturgeon said.
"The Scottish Government will use all the powers at our disposal to mitigate the impact of Brexit as we have been doing, for example, to provide support and advice to European nationals who have been treated utterly shamefully by this UK Government."
Mr Johnson this week formally rejected Ms Sturgeon's demands for a a transfer of power to Holyrood to allow a second referendum to be staged in the aftermath of the election result which saw the SNP record a landslide victory in Scotland.
Ms Sturgeon added: "Scotland deserves the right to decide it's own future and there's a really fundamental issue at stake in Scotland.
"It's not actually about whether or not Scotland should be independent - it's about who gets to decide. Should that be the Scottish people or should that be Westminster?
"It's also about whether the outcome of the general election is respected in Scotland, as the Tories rightly demand that it is respected elsewhere in the UK.
"The Conservatives of course are running scared of Scotland having that choice. I can understand why.
"But they will not stop it.
"Democracy denial will not prevail. The longer the Tories and perhaps others in this chamber persevere with the attempt to deny democracy, the more certain it becomes that Scotland will be an independent country."
The SNP leader raised fears that Scotland could see a "race to the bottom" in areas like workers rights, environmental standards and consumer rights as the UK seeks a trade deal with the US.
"This race to the bottom is a real concern," Ms Sturgeon added.
"We will do everything we can within our existing powers to protect Scotland against that, but the best way for Scotland to protect itself is to stop being at the mercy of Westminster Governments, particularly Westminster Tory Governments and to have he right to choose a better future."