SNP MP Angus Robertson said the Scottish Government intended to hold a referendum in October 2023 to allow the people of Scotland the “democracy to vote on independence”.
Opposition figures subsequently accused the SNP of "plucking dates out of a hat".
Launching a fresh independence campaign on Tuesday, Nicola Sturgeon said the people of Scotland would be allowed the opportunity to vote for independence with or without Westminster approval.
But Scottish Conservative MSP Craig Hoy said it was “deeply worrying” a “plan B” without a section 30 order could lead to “illegal referendum”.
The Scottish Tories chairman said: “It’s clear the SNP are ramping up their push for another divisive referendum.
“Nicola Sturgeon has come close to endorsing a plan to push ahead with an illegal vote and Angus Robertson doubled down on that today.
“This reckless push for another referendum will damage Scotland when all the focus should be on Covid recovery and the global cost-of-living crisis.
“The SNP are distracted by their obsession with independence once again. They're focusing on the wrong priorities and setting back Scotland’s economy and public services as a result.
“Our public services, especially the NHS, are still struggling after the pandemic. On top of that, the war in Ukraine has sent food and energy prices soaring, leading to an unprecedented squeeze on household incomes.”
Mr Robertson, the constitution secretary, denied the time period was an unrealistic goal as he said not every referendum was an “exact copy” of those that went before.
The First Minister has confirmed she will make a “significant” announcement to the Scottish Parliament later this month before the mid-year recess.
However, the UK Government under the leadership of Boris Johnson has insisted that ‘now is not the time’ for another referendum.
Speaking on BBC Good Morning Scotland on Wednesday, Mr Robertson said: “The First Minister made clear yesterday that she intends to make an announcement to the Scottish Parliament in the forthcoming weeks about a route map towards a referendum which we intend to hold next October.
"I am fully content that with the prospectus beginning to be rolled out, with the announcement that will follow on the route map on how that is going to be achieved, that we have a perfectly adequate window of opportunity both for legislation to be passed and for the opportunity for the people to scrutinise the prospectus that the Scottish Government will publish.”
Mr Robertson said he would not give a ‘sneak preview’ of what this referendum would involve after Presiding Officer Alison Johnstone chastised the MSP for the Government giving details on an independence statement to the media first before Parliament.
The Scottish Liberal Democrats accused the SNP of being “on another planet” when it came to talks of an independence vote.
Alex Cole-Hamilton, leader of the party, said: "Angus Robertson hurls insults at his opponents and insists that a vote will take place next autumn, but this week's polling shows that just 16 per cent of Scots think another vote is a top priority. He's not just out of touch, he's on another planet.
"Any MSP who thinks that independence trumps the cost-of-living crisis, the climate emergency and the shocking waits for child and adolescent mental health services needs to take a long hard look at themselves."
Mr Robertson said he saw "no reason” for the UK Government to deny a section 30 order, allowing for Holyrood to call for a referendum.
The constitution secretary said: “Scottish politics has a long history of the UK Government going, ‘no, no, no, yes’. That’s what happened in the run up to the referendum in 2014 and I still think we should work on the basis of the gold standard of democracy, which is that surely all of us involved in politics agree that when the people vote for something to happen in this country, it’s what should happen.”
Mr Robertson said, constitutionally, the UK Government should not block a vote on independence in 2023.
But Scottish Labour MSP Sarah Boyack accused Mr Robertson of "pie in the sky posturing", and claimed the SNP was "plucking dates out of a hat for another divisive referendum".
Scotland in Union, a campaign group for Scotland to remain in the UK, also accused the SNP Government of prioritising independence over other issues.
Pamela Nash, chief executive of Scotland in Union, said: “The overwhelming majority of people in Scotland do not want another divisive referendum next year.
“Angus Robertson is so obsessed that he thinks a second referendum is more important than improving our hospital, schools, or other public services.
“Scotland deserves better than being thrown into a constitutional fight that most people don’t want.
“As part of the UK we can unite communities and invest more in the NHS and schools so that we can build a fairer, stronger Scotland for everyone.”
However, as a pro-independence party, the Scottish Greens have supported the push towards the October 2023 date.
Scottish Greens MSP Ross Greer said: “The pro-independence parties won more votes and more seats at last year’s Scottish Parliament election than the anti-independence parties. By any normal democratic measure, we secured a cast iron mandate to hold a referendum.
“The Scottish Greens know that only with the full powers of a normal independent European country can we truly become the fairer, greener, outward looking society we aspire to be.”
Launching the first of a series of papers setting out the case to break away from the UK, Ms Sturgeon told a press conference in Edinburgh her Government had an "indisputable mandate" for a second independence referendum.
However, the First Minister conceded a future referendum faced challenges. If a referendum bill was introduced without Westminster agreement it could be challenged in the courts.