Kenny MacAskill, Scotland's former Justice Secretary, said the First Minister's announcement yesterday on preparatory legislation for a second independence referendum within the next two years along with a Citizens' Assembly did not "add up to another vote".
And he said independence activists expecting a quick referendum as "delusional".
In a highly critical article in The Scotsman, he wrote : "Holding another referendum’s problematic and those expecting an immediate poll delusional. However, mobilising the party and the wider independence movement’s essential and that’s been lacking. This new statement neither delivers the former, not encourages the latter.
"The talk of a poll before 2021 initially sounds positive but it’s heavily caveated and restricted by other factors. Will the UK have resolved its EU position by then? If that has been settled, can a poll even be carried out in time?
"But it allows her to reassure the party this weekend that she’s undaunted and the light undimmed."
However Finance Secretary Derek Mackay today said Ms Sturgeon was trying to keep the country's options open in the face of a Westminster Government that does "not give a damn for the people of Scotland".
He insisted the SNP leader was "fulfilling the mandate that if Scotland was taken out of the EU against Scotland's will that we would have a right to have a referendum".
Reflecting some criticism yesterday from the wider independence movement about Ms Sturgeon's statement yesterday, Mr MacAskill said all that had been announced was "another round of discussion and attempts at consensus building." And he warned the SNP against taking "the young and the poor" for granted at any new independence referendum.
"In all political parties, there’s a danger of taking your core support for granted and so it seems in the SNP. Those most supportive of independence last time were the young and the poor. Yet this strategy seems more geared towards corporate boardrooms or leafy suburbs.
"I could perhaps have some sympathy for that if it was shown to be working but it most certainly isn’t. Corporate support seems at an all-time low and the disdain that even my good friend the financier and Yes supporter Peter de Vink has is evident."
Financier de Vink, a friend of former First Minister Alex Salmond, was one of the leading business figures to support independence in 2014. He recently launched a savage attack on Nicola Sturgeon's tax policy, saying she is 'only interested in soaking the rich'.
Mr MacAskill added: "As Nicola Sturgeon pursues her personal crusade to make Scotland the most gender equal, trans-friendly state in the universe, complaints are growing about public services. Those who also seek change are speaking out as Extinction Rebellion shows. The SNP is in danger of positioning itself away not just from its own bedrock support but from those who could be mobilised to back it.
"The EU elections will mask the issue, as the SNP will do well with a relatively low turnout and having a clear position on Brexit. Later elections will be different if the poor decide the SNP are not for them and the young that they are not radical enough."
However speaking on BBC Radio Scotland's Good Morning Scotland programme, Derek Mackay said: "Scotland has to have its options open, we have to have the right to choose our future rather than leave it in the hands of Westminster, who have shown they do not give a damn for the people of Scotland."
On the offer of cross-party talks, he said Ms Sturgeon was "trying to reach out to other opposition parties, to say 'if not this then what' and try to identify a way forward".
And he said: "We're putting in the foundations to enable referenda to happen and in terms of independence ensure that we have that choice in this term of the Scottish parliament, fulfilling a mandate that ultimately the SNP has won elections on."