"In such circumstances, any continued Tory attempts to block the people of Scotland having a choice on their future, when the options are clear, and on a timescale determined by the Scottish Parliament, would be democratically unsustainable".
The SNP, which claims to be the only real opposition to the Tories in Westminster, won 56 of Scotland's 59 electoral districts in 2015, some of which the Conservatives are aiming to claim on June 8.
"While the Tories are set to plunge Britain into Brexit without a clear plan, a vote for the SNP will give us a strong hand in the Brexit negotiations to ensure Scotland's interests - on jobs and our economy - will be heard at the top table".
In "challenging economic times", she said Brexit - and "especially an extreme Brexit" - put in danger the progress that is being made.
Speaking to Sky News in Moray in Scotland, Scotland's First Minister repeatedly refused to say if a promise of another Scottish referendum would be a precondition of any deal.
After 62% of Scots voted to keep the United Kingdom in Europe, Ms Sturgeon instructed Scottish Government staff to start drawing up the necessary legislation for another vote on the issue.
A vote for the SNP, Sturgeon promised, "would make it impossible to continue ignoring those voices" that called for a "compromise" to allow Scotland to remain in the single market.
"There is just too much at stake for Brexit simply to be imposed on Scotland", she said.
In September she had a +16 rating, but this is now down 43 points to -27, with nearly twice as many disapproving of how she has done her job compared to those approving of it.
The Labour leader, who has already ruled out any agreement with the SNP, spoke out on the issue again on Monday with less than two weeks to go to the General Election.
Nicola Sturgeon can talk about opposing austerity all she likes, but the reality is that the SNP has cut £1.5bn from local services like schools and care of the elderly.
"They are political dogma - an ideology".
But asked yesterday about the principle of holding a second independence referendum, the Labour leader said: "What I've said is that if the Scottish Parliament and the Scottish people want a referendum, they have the right to do that, that was the whole point of the devolution agreement of the 1990s".
Rival candidates this time say Sturgeon's stance on Brexit and independence has alienated previous SNP voters, who are now backing the Tories, Labour and the Liberal Democrats.