Scottish Tories are planning to walk out if the SNP press ahead with plans for a second referendum
Tories are prepared to “boycott” any bid to introduce a Bill paving the way for a poll in the face of opposition from Westminster.
Ms Sturgeon wants a re-run of the 2014 ballot between autumn 2018 and spring 2019 despite Prime Minister Theresa May’s decision to block one.
The SNP leader has indicated that she will outline the “next steps” in her constitutional battle after the Easter recess.
Some sources have indicated options could include holding a “consultative” plebiscite without UK Government consent or introducing a Referendum Bill at Holyrood without securing a “section 30 order” first.
If Presiding Officer Ken Macintosh allows it to proceed, it would fall to Mrs May to ignore it or challenge it in the courts.
But the Bill could still be introduced at Holyrood even if Mr Macintosh rules it to be outside the competence of the Parliament.
Ministers could attempt to use a little-known procedure to bring it forward regardless, without his consent.
We are not going to participate in anything that is outside the Parliament’s remit
Scottish Tory source
Mrs May has insisted she will not allow a referendum during the timescale requested by the First Minister because it would impact on Brexit negotiations.
But Ms Sturgeon has claimed her warning that “now is not the time” is a “holding position”.
Tory sources insisted the party would “boycott any attempt to create constitutional conflict” and hit out at “a cynical ruse to stoke up grievance”.
Get Quotes on Home Insurance
Nicola Sturgeon plans to hold a new referendum on Scottish independence before by spring 2019
One said: “We are not going to participate in anything that is outside the Parliament’s remit.”
An SNP spokesman said: “If the Tory intention is to try to block indefinitely a referendum, that would be utterly undemocratic.
“It will only be a matter of time before the Tories realise that their attempts to diminish and ignore the Scottish Parliament will backfire on them badly.
Nicola Sturgeon's most outrageous quotes Sun, April 9, 2017
The nationalist chief always has plenty to say
1 of 10
'Men – the colour of their tie is the most difficult decision they have to make every day'
“The First Minister will set out next steps in the coming weeks.”
The move came as the First Minister came under pressure to pressure to reveal the findings of a consultation on the issue.
Her government has yet to publish the results of a public discussion on its Draft Referendum Bill, which closed to submissions three months ago.
The SNP leader is reported to be planning to outline her 'next steps' after the Easter recess
It attracted some 7,500 responses and ministers have said they “will be published in due course”.
Polls suggest there is little appetite for a second referendum and unionist parties claim the issue is being repeatedly raised while canvassing.
Scottish Lib Dem leader Willie Rennie said: “If the responses to the consultation are as colourful on the doorstep it is no surprise the SNP is reluctant to publish.
“The First Minister should publish the responses before she takes one more step towards an independence referendum.”