A paper, which has been published as the party's National Executive Committee meets on Monday, says that if the UK Government does not agree to a section 30 order, transferring power to Holyrood for a referendum, the issue should be the focus of the coming Scottish election campaign.
The paper has been penned by SNP Inverclyde councillor Chris McEleny, who has been a long-term advocate within the party of a ‘Plan B’ approach to pressing ahead with a Holyrood-sanctioned repeat of the 2014 vote on leaving the UK.
"The Scottish Government must issue a deadline of 31st March 2021 to the UK Government, in advance of the Scottish general election, to agree to a section 30 request," the paper states.
"In the event that the UK Government do not agree to the above, then pro-independence parties should unambiguously state that in the event of a pro-independence majority of MSPs being elected to the Scots Parliament in the Scottish general election, there will be a referendum on Scottish independence – as sanctioned by the Scottish Parliament, which will be given popular legitimacy by the Scottish electorate via the mandate given in the 2021 Holyrood elections."
If a pro-independence majority is returned in May, Mr McEleny says the newly-formed Scottish Government should then begin preparations to hold a referendum – without the current requirement of seeking the approval of the UK Government via a section 30 Order.
The Scottish Government wants to stage a referendum in response to the Brexit vote, which saw a majority of Scots vote to remain in the EU, but the weight of votes south of the Border swung the outcome in favour of Leave.
The demand for such a ‘Plan B’ approach has caused splits within the SNP.
First Minister Nicola Sturgeon does not back such an approach, insisting Mr Johnson will be forced to relent on the referendum issue, if another pro-independence majority is returned in May.
But the paper states: "By the date of the Scottish Parliament election in May 2021, the UK Government will have sustained opposition to agreeing to a referendum on Scottish independence after several electoral mandates having been secured since 2016 to hold such a referendum."
It adds: "A referendum deemed lawful by Scotland’s Lord Advocate, and sanctioned by Scotland’s Parliament as per the mandate of the Scottish people, will be a competent and lawful referendum."
The SNP will stage a National Assembly on January 24 that will consider “tactics and strategy" on the route to independence.
It comes as consistent polling throughout last year shows that a clear majority of Scots now back leaving the UK.
Ms Sturgeon has already pledged to publish legislation before the end of the current Holyrood term in April setting out the "terms and timing" of a future referendum on leaving the UK.
The First Minister has also previously said that she would not rule out a legal challenge to test whether Holyrood could stage a referendum.