Mr Johnson has repeatedly ruled out another vote on the issue, just six years after Scots last went to the polls.
The SNP argues that victory in May’s Holyrood elections would guarantee the party a mandate for a second referendum.
This weekend the First Minister of Scotland described the goal of independence as “in sight”.
She also said that she wanted to hold a vote in the “early” years of the parliament’s next term.
But Mr Johnson remains a potential stumbling block.
Ms Sturgeon told the BBC’s Andrew Marr programme that she took instruction from the people of Scotland not from the prime minister.
She added: “I’m going to do the old fashioned, traditional, democratic thing and ask the people of Scotland in May for their authority for a legal referendum to allow the people of Scotland to choose their own future.
“It is not for Boris Johnson to stand in the way of people choosing their future”.
She added: “I’m a democrat”.
Some within the SNP want the party leadership to organise a vote without the sanction of Westminster, in the belief the international community cannot ignore a result that can be demonstrated to reflect the will of the people.
But today the party’s Westminster leader will tell SNP members must “keep heart, keep the heid and keep the faith” as they push for independence.
Ian Blackford will issue a call for unity at his party annual conference, following calls for more internal debates including on how best to accelerate the cause of Scottish independence.
