Humza Yousaf will immediately begin independence negotiations with the UK Government if his party wins more than half of the seats at the next general election.
A motion, signed by the First Minister, would see the SNP treat a majority of Scottish seats at Westminster as a mandate for leaving the UK.
The plans were first laid out by the SNP leader in June at the party’s independence convention but will be formally voted on by members at its October conference.
It proposes that in the event the party wins the most Scottish seats at the next UK general election, the Scottish Government will be “empowered to begin immediate negotiations with the UK Government to give democratic effect to Scotland becoming an independent country”.
At that point, the SNP would publish detailed conditions for its negotiations on leaving the union – including a draft legal text on the transfer of powers between Westminster and Holyrood.
The motion the party says will also “conduct a nationwide consultation on a draft interim constitution, which would be the founding document of an independent Scotland”.
And it will “prepare the ground for Scotland to become an independent member state of the EU, by establishing an envoy position, who would be a representative of the Scottish Government in Brussels.”
The motion, also signed by SNP Westminster leader Stephen Flynn, proposes making “vote SNP for Scotland to become an independent country” the first line of the party’s manifesto.
The next general election is expected sometime in 2024.
The plan follows a similar pitch by former first minister Nicola Sturgeon.
She introduced the idea of a “de facto referendum” after the UK Supreme Court ruled that Edinburgh does not have the power to hold a referendum on the constitution without London’s permission.
Sturgeon said that if the SNP won the most votes at the next general election she would begin negotiations on independence.
However, Yousaf’s strategy has now changed this to winning the most seats.
Critics argue that this means the SNP could lose 18 of its 48 MPs at the next election and still claim it as a mandate for independence negotiations.
Both plans come as successive UK Governments repeatedly refuse to grant permission to hold another Scottish independence referendum.
The SNP has won a majority of seats at the last three Westminster elections. Only in 2015 did the party win 50% of the vote when it took 56 out of Scotland’s 59 seats.
Yousaf’s plan has been criticised by a former SNP leader as well as unionist parties.
Alex Salmond, who now leads the Alba Party, said: “No one seriously believes that proposing a majority of seats as an independence mandate is at all credible.
“Given that Westminster has been allowed over repeated elections to dismiss a majority of SNP seats as a mandate for a mere referendum, why on earth would they concede it as a mandate for negotiating independence itself.”
Alex Cole-Hamilton, leader of the Scottish Lib Dems, said it seemed like Flynn and Yousaf had “lost the plot”.
“They had a gold standard referendum and lost it but now they want to invent a crackpot alternative that allows them to lose a bunch of seats but still break up the UK with a fraction of the vote,” he said.
A spokesperson for the SNP said: “Humza Yousaf outlined a general election strategy for the SNP at the party’s convention on independence in June. The core of that strategy was to ensure that the SNP contests the next UK general election on the issue of independence.”
The spokesperson said this had been discussed by SNP members at eight regional assemblies over the summer, with the motion “drafted to reflect the feedback from that democratic process, and respect the views of members from across the country”.
The spokesperson added: “The resolution from Humza Yousaf and Stephen Flynn has now been published, and is open to amendment before it is debated at annual conference in October.”
The UK Government has been approached for comment.