Joanna Cherry, said the Scottish Parliament should pass a bill to hold a referendum to "move us away from the current impasse" and she said she believed the Scottish Government would win a legal challenge should the Prime Minister go to court.
Her comments came after a new poll showed voters backed a legal battle with Mr Johnson if he continues to refuse to grant a Section 30 Order, the procedure which transfers the power to hold a second referendum from Westminster to Holyrood.
And they underline the split between the SNP gradualists, such as Nicola Sturgeon who has said that any second referendum would have to follow the "gold standard" as set out in the 2014 vote, and those who want more immediate action.
According to the Panelbase poll conducted for the ScotGoesPop! blog, supported by The National newspaper, more than half of those asked believe the Scottish Parliament should legislate to hold a referendum if Westminster does not agree to it and then allow the courts to decide if Holyrood has the legal capacity to take the unilateral move.
The poll question said: “There are differing legal opinions on whether the Scottish Parliament currently has the power to hold a consultative referendum on independence without Westminster’s permission.
“If the UK government continues to refuse to give permission, do you think the Scottish Parliament should legislate to hold a referendum and then allow the courts to decide whether it can take place?”
Of those who expressed an opinion, 56 per cent agreed with the statement, with 44 per cent saying no. When ‘don’t knows’ were included, 50 per cent said yes and 39 per cent said no.
However First Minister Nicola Sturgeon has been clear that she would not back a "wildcat referendum" and would continue to push for a Section 30 Order. At the same time, she said there would be “no guarantees” if the legal position of whether the Scottish Parliament could hold its own vote was tested.
Today on Twitter Joanna Cherry said she welcomed the poll and added: "I believe that Holyrood passing a bill to hold a referendum could be part of a multi-faceted strategy to move us away from the current impasse and stop the constant and unproductive talk about Section 30 orders and seeking “permission” to act from Westminster.
"The balance of legal opinion is that we might well win any court challenge and I don’t believe that losing would set us back any further than where we are just now. Boris Johnson should be put on notice that we have options and we are not afraid to push forward.
"After three great independence polls it’s time to consider our options. The timing of taking the consultative referendum route and thus inviting a legal challenge will be crucial. However I agree that ...now is the moment to begin the preparations. To tell Johnson “see you in court” if he continues to block Scotland’s demand for indyref2.”
SNP depute leader Keith Brown also welcomed the poll. “This new poll demolishes the Tories’ tired claim that there is no demand for an independence referendum – the reality is that people want one and they want it to be made in Scotland, not in Westminster.
“Support for independence is growing every day, with the latest polling showing a majority for Yes – and the longer the Tories try to block a referendum the higher support for independence will rise.”
The idea of a legal route to a second independence referendum has been raised by a number of senior SNP politicians.
Alex Neil, who has called for Holyrood to hold its own consultative vote if such a move is declared legal, said: “If Boris Johnson continues to deny the right of the Scottish people to decide their own future, clearly we need to look at other options.
“But I agree with the First Minister, we have got to give democracy every chance, so if we get to 2021 and the SNP win an overall majority on the back of a mandate for indyref2, then democratically and morally Johnson cannot say no."
However the idea of a consultative referendum was immediately rejected by opposition parties. Scottish Liberal Democrat leader Willie Rennie, said Ms Cherry's comments were "a direct challenge to Nicola Sturgeon. She's made clear its not her preference and a wildcat referendum is that last thing we need."
Scottish Labour's Rhoda Grant added: "It would be crazy and the SNP know that. People are so fed up with referendums they would reject that, and actually the support for independence, given we have a Boris Johnson government in Westminster, should be stronger than it is."
Liam Kerr of the Scottish Conservatives said it was times to "end uncertainty and constitutional wrangling", and for the SNP to "concentrate on the day job".
And Scottish Greens co-convener, Patrick Harvie, who support independence, also cast doubt on the idea. He said: "A referendum is far clearer if it stays out of the courts, that's the way to create mess, we need to carry on making the case in terms of principle."
Pamela Nash, chief executive of Scotland in Union, also rejected Ms Cherry's suggestion and said: “The majority of people in Scotland don’t want a divisive second independence referendum, and want the SNP Government to get on with the job it was elected to do.
“Trying to break up the UK via the back door through an unofficial contest is simply not acceptable and would end up in a huge cost to the public purse - taking money away from lifeline services. Scotland deserves better.”