Nicola Sturgeon has refused to rule out taking legal action if Boris Johnson is returned to Downing Street and blocks a second Scottish independence vote.
The First Minister and SNP leader made clear she would not hold a Catalan-style unauthorised ballot on leaving the UK.
But with Mr Johnson having repeatedly stated he will not permit a second ballot on independence while he is prime minister, she was pressed on what her options would be during a television interview.
Ms Sturgeon stressed a majority Conservative Government was "not inevitable" after the December 12 General Election and said whoever ends up in Number 10 must "respect the will of the Scottish people".
Speaking on BBC Breakfast, the First Minister said: "I do believe whoever is in Downing Street, they have a duty to respect the will of the Scottish people."
If Mr Johnson remains as PM and continues to refuse to grant permission for a fresh vote on independence, she pledged she would "set out how I intend to cross that bridge then".
"We're in an election campaign right now," Ms Sturgeon said. "Whatever the polls might be suggesting, and they look as if they are narrowing a bit, a Tory majority isn't inevitable."
Pressed on whether the Scottish Government would mount a legal challenge if Westminster continued to refuse to allow a referendum, or would stage an unofficial ballot, Ms Sturgeon said the vote would have to be "legitimate".
She said: "I've made my view quite clear on an unofficial referendum, I think a referendum has to be legal and accepted because I'm not in the business of just having a referendum, I want Scotland to become independent so you have to have a process of doing that that is going to be recognised as legitimate.
"Beyond that though I will consider all options.
"But the first option is making sure we don't get into this scenario because Scotland is playing its part in making sure Boris Johnson is not in this position of being able to lay down the law to Scotland or anybody else."
She said whatever the result of the election "SNP MPs will always push Scotland's case and fight for those progressive policies, whatever the arithmetic is in the House of Commons".
But Ms Sturgeon said her party's influence would be "increased in strength" if there was a hung Parliament leaving "Scotland is holding the balance of power".
She said the central point in the election for Scotland was: "Do we have our future decided for us by the likes of Boris Johnson and the people who are pulling his strings, like Nigel Farage and Donald Trump, or do we decide our future for ourselves and the kind of country we want to be?"
Ms Sturgeon said: "If you are asking me to predict, I believe very, very strongly, particularly after the last few years, that given that choice in the future Scotland will choose to be independent."
