Scottish First Minister Nicola Sturgeon has said a second referendum on Scottish independence before 2020 is "highly likely".
Speaking on ITV's Peston on Sunday, Ms Sturgeon said events since Britain voted to leave the EU has made her even more resolved to push through another referendum.
The First Minister said she is "absolutely serious" about exploring other options, but insisted that the prime minister must show Scotland's interests within the UK can be protected.
"If Scotland really is an equal partner in the UK [and] Theresa May is serious about protecting the UK, then it's time for her to turn those words into action and actually demonstrate that Scotland's voice is heard," Ms Sturgeon said.
The first minister also attacked Theresa's May for not sharing her position on negotiating Britain's exit from the EU, saying her approach is "unsustainable and unacceptable".
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Nicola Sturgeon has accused Theresa May of ignoring Scotland's "voice and interests" as Britain prepares to leave the European Union.
The prime minister told the Conservative party conference in Birmingham there is "no opt out from Brexit" and she will "never allow divisive nationalists to undermine the precious union between the four nations of our United Kingdom".
"We will negotiate as one United Kingdom and we will leave the European Union as one United Kingdom," said Mrs May.
But the First Minister of Scotland hit out at Mrs May's remarks, after the majority of people in Scotland voted to remain in the EU, unlike the rest of the UK.
PM going out of her way to say Scotland's voice and interests don't matter. Strange approach from someone who wants to keep UK together.
Ms Sturgeon said on twitter the prime minister was "going out of her way" to say that "Scotland's voice and interest don't matter".
She added that Mrs May's "approach" was "strange" for "someone who wants to keep the UK together".
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Theresa May underlined the importance of keeping Britain united by making her first official visit to Scotland.
The Prime Minister met First Minister Nicola Sturgeon, and said she will listen to options to satisfy Scotland's wish of keeping close ties with Europe.
ITV News' Deputy Political Editor Chris Ship reports:
Scottish First Minister Nicola Sturgeon has said she is determined to consider all options to protect Scotland's relationship with the EU.
Ms Sturgeon said her meeting with British Prime Minister Theresa May on Friday was "constructive", adding that she was pleased Mrs May was willing to consider options raised by Scotland.
"It was very important today to get a commitment from the prime minister...to listen to options that the Scottish government brings forward," Ms Sturgeon said.
"There is an agreement that Scottish government officials will be very closely involved in discussions."
Ms Sturgeon said Scotland may have to consider becoming independent in order to protect its with membership of the EU, but insisted she would "consider all the options along the way".
The prime minister knows, as everybody else knows, that a second independence referendum is of course on the table because Scotland finds itself now in the position of facing exit from the EU against our will.
Article 50 will not be brought forward until there is a UK-wide approach, Theresa May has said.
Speaking after meeting with Scottish First Minister Nicola Sturgeon, Mrs May said: "I'm willing to listen to options and I've been very clear with the first minister today that I want the Scottish government to be fully engaged in our discussions.
"I have already said that I won't be triggering Article 50 until I think that we have a UK approach and objectives for negotiations - I think it is important that we establish that before we trigger Article 50."
The newly appointment British prime minister has used her "Brexit is Brexit" mantra to reassure the majority of the British public who voted to leave the EU that she is serious about negotiating Britain's exit from the bloc.
Theresa May greeted Scotland's First Minister Nicola Sturgeon as she arrived in Edinburgh on Friday.
The prime minister is to hold a meeting with Sturgeon to show her commitment to preserving the "special union" of the UK, she said ahead of her visit.
Last month, Mrs Sturgeon said a second independence referendum was "highly likely" after the UK voted to leave the European Union.