The First Minister will tell SNP delegates at the party’s spring conference in Aberdeen that Westminster must not be allowed to deny a fresh vote.
Nicola Sturgeon’s speech will come just hours after Gordon Brown has called for Holyrood to be handed a raft of new powers after Brexit as idea of a “third option” he believes could unite the country.
The former prime minister said a new form of federal home rule is needed to offer an alternative to the division between Holyrood and Westminster.
However, Ms Sturgeon is likely to reinforce her demand for a second independence referendum in a high-profile speech.
Prime Minister Theresa May says the “time is not right” to seek public backing to quit the UK.
But Ms Sturgeon will say blocking the will of the Scottish Parliament would “shatter beyond repair” claims Scotland is an equal partner in the Union.
Ms Sturgeon will say: “To stand in defiance of it would be for the Prime Minister to shatter beyond repair any notion of the UK as a respectful partnership of equals.”
The First Minister shocked the UK Government with her announcement on Monday that she wants a second independence referendum to be held between autumn 2018 and spring 2019.
With the UK having voted to leave the European Union in 2016 and Scotland voting to stay part of the bloc, she will insist the future “looks very different” than it did in 2014 when Scotland said No to independence.
Closing the SNP conference, Ms Sturgeon will say: ” We know change is coming. The EU referendum has made sure of that. The only question is what kind of change.”
She will insist Scots are “not powerless” and can “still decide which path we take”.
“Next week… we will ask the Scottish Parliament to agree that the Scottish people should have the right to choose our own future.
“We will ask Parliament to agree that this choice should be exercised at a time when we know the terms of Brexit but before it is too late to take a different path.
“And we will ask Parliament’s permission to seek the legal authority that will allow the people of Scotland to have that choice.
“If a majority in the Scottish Parliament endorses that position, the Prime Minister should be clear about this. At that point a fair, legal, agreed referendum – on a timescale that will allow the people of Scotland an informed choice – ceases to be just my proposal, or that of the SNP. It becomes the will of the democratically-elected Parliament of Scotland.”
She will tell the Prime Minister: “If her concern is timing then – within reason – I am happy to have that discussion.”
Scottish Conservative chief whip John Lamont said: “Nicola Sturgeon said as late as Thursday that a referendum after April 2019 would be ‘too late’. Now she has changed her mind and appears to be trying to engage in some kind of horse-trading with the UK Government.
“The future of Scotland is not a game. It is time for the First Minister to act responsibly over our future.”
Ex-Labour leader Mr Brown, an architect of the 2014 “vow” promising Holyrood more powers in the event of a No vote to independence, gave his speech at the Festival Of Ideas in Kirkcaldy, Fife, He proposed a range of controls be passed to the Scottish Parliament after Brexit.
These include the setting of VAT rates, the power to sign international treaties, and controls over agriculture, fisheries, environmental regulation, employment and energy.
He said: “You can call it a more federalistic option, you can call it in the more traditional way Scottish home rule, you can call it federal home rule. I’m calling it the third option, a Scottish patriotic way forward.”
He added: “I think it will become clear over the next few months that the third option, that Scotland has more powers as part of a federal agreement with the UK, a Scottish home rule that gives us the powers to make decisions in important areas but does not deprive us of the co-operation we need, will be the best option.”
Mr Brown said he believes it can become the “unifying option for our country.”
The former PM also called for the repatriation to Scotland of £800 million of money now spent by the European Union, and proposed the Bank of England becomes the Bank of England, Scotland, Wales and Northern Ireland with fully staffed representation in Scotland ”to reinforce the fact that the pound is for everyone”.
He said changes are needed as we cannot continue with the status quo, but that independence is not the answer.
Mr Brown said: “The world has changed but not the way the SNP want it to be. The world has changed and we have to face up to post-Brexit realities. It doesn’t make the case for independence stronger, it makes it weaker.”
MSPs are expected to back the First Minister’s call for a Section 30 order to be granted when Holyrood votes on the issue on Wednesday.
That would then see the Scottish Parliament formally request that Westminster grants it the authority to hold a legally binding referendum.
