The SNP leader addressed a conference in Edinburgh organised by the Institute for Public Policy Research (IPPR) think tank just over a month on from the EU referendum.
The First Minister has previously said a second independence vote was “highly likely” in order to protect Scotland’s place in Europe, but promised to explore other ways of achieving this.
She said independence may emerge as the option which offers “the greatest certainty, stability and the maximum control over our own destiny”.
Ms Sturgeon also said UK politicians failed to prepare for a vote for Brexit, describing it as “one of the most shameful abdications of responsibility in modern political history”.
“In seeking to chart a way forward for Scotland, independence wasn’t my starting point - that remains the case,” she said.
“Protecting Scotland’s interests is my starting point, and I am determined to explore all options to do that.
“But I am equally clear about this - if we find that our interest can’t be protected in a UK context, independence must be one of those options and Scotland must have the right to consider that option.
“That’s why we will take the preparatory steps to make sure it is an option open to the Scottish Parliament if the Scottish Parliament considers it necessary.
“I don’t pretend that independence would be straightforward. It would bring its own challenges as well as many opportunities.
“But consider this - the UK that we voted to stay part of in 2014, a UK within the EU, is fundamentally changing.
“The outlook for the UK is uncertainty, upheaval and unpredictability.
“In these circumstances it may well be that the option that offers us the greatest certainty, stability and the maximum control over our own destiny is independence.”
IPPR director Russell Gunson has said the Scottish Government lacks “a genuine commitment to the UK”, so it is up to unionists to present options for Scotland’s EU future if they want to protect the UK - which both governments must pursue with “equal vigour”.
Addressing an audience of business leaders, charities and public-sector organisations, Ms Sturgeon reflected on the EU referendum campaign and the result.
Voters in Scotland were 62% against leaving the EU despite a UK-wide win for the Leave campaign.
She also spoke about how to handle negotiations regarding Scotland’s future in the EU.
Ms Sturgeon said: “I am determined that we find or create the options that best-preserve the five key interests that depend on our relationship with the EU.
“Our democratic interests - the need to make sure Scotland’s voice is heard and our wishes respected.
“Our economic interests - safeguarding free movement of labour, access to a single market of 500 million people and the funding that our farmers and universities depend on.
“Our interests in social protection - ensuring the continued protection of workers’ and wider human rights.
“Our interest in solidarity - the ability of independent nations to come together for the common good of all our citizens, to tackle crime and terrorism, and deal with global challenges like climate change.
“Our interest in having influence - making sure that we don’t just have to abide by the rules of the single market but also have a say in shaping them.
“Democracy, economic prosperity, social protection, solidarity and influence - these are the vital interests that we now seek to safeguard.
“They are not abstract. They are real and they matter - for jobs, the economy, trade, investment and living standards.
“That’s why my task today and tomorrow, and throughout the length of the coming negotiations, will be to protect Scotland’s relationship with and interests in the European Union, and to explore every avenue and every option for doing so.”
The First Minister also criticised what she described as a “lack of leadership” from the UK Government and those leading the campaign to leave the European Union (EU) in the days following the referendum result.
She said after the vote it had been the “the job of politicians not to pretend somehow that we instantly had all the answers but to give a sense of direction, to try to create some order out of the chaos”.
“That’s what I was determined to do for Scotland and I assumed that UK politicians would do likewise,” she said.
“It turned out I was wrong about that.
“In fact, the absence of any leadership and the lack of any advance planning both from the politicians who proposed the referendum and from those who campaigned for a leave vote surely must count as one of the most shameful abdications of responsibility in modern political history.”
Murdo Fraser, shadow finance secretary, said: “It is right that the Scottish Government should be examining how best to further our interests as the United Kingdom begins negotiations with the European Union.”
“However, as two million Scots agreed in 2014, leaving the United Kingdom is not in Scotland’s interests, and the Scottish Government should therefore end its flirtation with yet another divisive referendum on independence. Its focus as we enter this crucial period should instead be to work with the UK Government to get the right deal for families and firms across Scotland. “
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