Holyrood is under attack from “emboldened” Tories who want to “claw back” powers from MSPs, Nicola Sturgeon says.
The First Minister said “a now powerful Westminster faction” sees leaving the EU as an “opportunity to rein in the Scottish Parliament”.
She added the failure of UK ministers to compromise over Brexit means an independence vote “may be the only way” that Scotland’s voice is heard.
In a speech to the David Hume Institute, she said the Tories are threatening to water down Holyrood, despite assurances that Brexit would see a transfer of powers from Brussels to Edinburgh.
“It is clear from their statements that even elements of farming and fishing policy – which have been a wholly devolved competences from day one – now risk being taken back to Westminster,” she said.
“It would be a gross betrayal of the claims and promises made during the EU referendum campaign.”
Scotland voted to Remain with a 62% majority, but is set to be taken out of the EU on the strength of Leave votes elsewhere.
Ms Sturgeon has repeatedly said since last June’s vote that a second plebiscite on independence is “highly likely”.
The Scottish Government has put forward proposals for Scotland to stay in the European single market – but no deal has been struck just days before the triggering of Article 50.
Scottish Conservative leader Ruth Davidson said the UK Government’s white paper on Brexit makes clear that no powers will be removed from Holyrood and more decisions will be devolved.
“This hyperbole from the First Minister takes synthetic grievance to a whole new level. Frankly, she sounds shrill,” she added.