The prime minister’s spokesman said “now is not the time” for another campaign to remove Scotland from the United Kingdom.
The Downing Street snub came as Sturgeon unveiled her latest campaign to hold “Indyref2” by the end of next year.
The first referendum took place in 2014, when the pro-UK side won by 55 per cent to 45 per cent.
In order to hold a legal referendum, the UK government must give the Scottish Parliament the power to stage one - known as a Section 30 order.
The first minister said the fact there is a majority of pro-independence MSPs in the Scottish Parliament meant there was an “indisputable democratic mandate” for another vote.
But the PM’s spokesman said: “The UK government’s position is that now is not the time to be talking about another referendum.
“We are confident that the people of Scotland want and expect their governments to be working together to focus on issues like the global cost of living challenges, like the war in Europe and the issues that matter to their families and their communities.”
He added: “The position on the referendum remains unchanged. It’s not something the prime minister believes the public want either government to be focused on at a time when there are other challenges facing them right now
“First and foremost we want to continue to work with the Scottish government on those issues that are affecting the public right now.”
The Scottish government today published a new document entitled ’Independence in the Modern World. Wealthier, Happier, Fairer: Why Not Scotland?, which they said “sets the scene” for the debate about Scotland’s future.
Speaking at a press conference in Edinburgh, Sturgeon said it was “time now to set out and debate” the case for Scotland to leave the UK.
She said: “After everything that has happened - Brexit, Covid, Boris Johnson - it is time to set out a different and better vision.
“It is time to talk about making Scotland wealthier and fairer. It is time to talk about independence and then make that choice.”
Sturgeon said a second referendum “must be lawful” but that if the UK government “had any respect at all for democracy” it would not block one from taking place.
“My duty, as the democratically elected first minister, is to the people of Scotland, it is not to Boris Johnson or to any Tory prime minister,” she said.
“This is a UK Government that has no respect for democracy. That means if we are to uphold democracy here in Scotland we must forge a way forward, if necessary, without a section 30 order.”
But raising the prospect of holding a wildcat referendum, Sturgeon added: “If we are to uphold democracy here in Scotland we must forge a way forward, if necessary, without a section 30 order.”