Setting out “as best as I can my reasons”, Ms Sturgeon said: “First, though I know it will be tempting to see it as such, this decision is not a reaction to short-term pressures. Of course there are difficult issues confronting the government just now, but when is that ever not the case.

“I have spent almost three decades in frontline politics, a decade-and-a-half on the top or second-top rung of government.

Nicola Sturgeon has said her decision to resign Scotland’s First Minister “is not a reaction to short-term pressures”.

“When it comes to navigating choppy waters, resolving seemingly intractable issues, or soldiering on when walking away would be the simpler option, I have plenty of experience to draw on.

“So if this was just a question of my ability or my resilience to get through the latest period of pressure I wouldn’t be standing here today, but it’s not.

“This decision comes from a deeper and longer-term assessment. I know it may seem sudden, but I have been wrestling with it, albeit with oscillating levels of intensity for some weeks.”

Ms Sturgeon said serving as First Minister of Scotland had been a “privilege beyond measure” as she announced her resignation.

She said: “I am proud to stand here as the first female and longest serving incumbent of this office and I am very proud of what has been achieved in the years I’ve been blessed to do this.

“However, since the very first moment in the job, I have believed that part of serving well would be to know, almost instinctively, when the time is right, to make way for someone else.

“And when that time came, to have the courage to do so, even if to many across the country and in my party, might feel it too soon.

“In my head and in my heart I know that time is now. That it is right for me, for my party and for the country. And so today I am announcing my intention to step down as First Minister and leader of my party.”

Ms Sturgeon has been First Minister since November 2014, when she took over from Alex Salmond following the independence referendum.

It is not yet clear if she will stand down immediately, or continue in the role until a new SNP leader is elected.

Ms Sturgeon will leave office as the longest serving and first female first minister since the creation of the Scottish Parliament, a time which saw her lead the SNP to repeated election victories at UK, Scottish and local level.

The First Minister, however, has been mired in controversy in recent months as her Government sought to push through gender reforms, only for them to be blocked by the UK Government.

But Ms Sturgeon stands down without realising her key political mission – independence for Scotland.

Her party will meet next month to discuss the holding of treating the next UK election as a “de-facto referendum”, with more than 50 per cent of the vote being considered a mandate to begin negotiations for Scotland to become an independent country.

Jackie Baillie, Dumbarton constituency MSP, pictured right, said: “Both Nicola Sturgeon and I were elected to the Scottish Parliament in 1999 and I have watched her career in opposition and in government.

“As Scotland’s longest serving First Minister she deserves our thanks for her public service, particularly during the pandemic.

“I join with the rest of my party in wishing her well for the future – whatever that may hold.

“Her successor has a tough job ahead as her legacy is one where the NHS is in crisis, educational attainment is going the wrong way and life expectancy has fallen and is now the worst in the UK.

“We need unity not continuing division in Scotland and we need fresh ideas and energy to tackle the big challenges ahead.

“The country is crying out for change, to tackle the cost of living crisis, to grow the economy and to recover our NHS. Scottish Labour is working hard to be the change that Scotland needs.”

Scottish Conservative leader Douglas Ross MSP, left,  said: “Whatever our differences, it is right we recognise that political leadership is always demanding and takes its toll on a person and their family.  I am glad Nicola Sturgeon has recognised this is the right time to go.

“However, at this time, we cannot ignore that she has presided over a decade of division and decay in Scotland.

“Instead of trying to unite the country in the wake of the 2014 referendum, Nicola Sturgeon refused to accept the result. Her entire tenure as First Minister has been characterised by relentless agitating for another vote on separation – governing in her party’s interests, rather than Scotland’s.

“As a result, Scotland has been in a state of constitutional paralysis ever since – divided and unable to move on from the Groundhog Day of 2014 and its toxic legacy, despite the wish of the majority of Scots to do just that.

“The SNP Government now needs to use this opportunity to focus on the Scottish people’s real priorities, especially the cost-of-living crisis, supporting our NHS and rebuilding our public services.”

Republic of Ireland Taoiseach Leo Varadkar paid tribute to Ms Sturgeon following her decision to stand down as first minister.

He said: “I had the pleasure to work with Nicola through the British Irish Council and met her on a number of occasions.

“I also welcomed her to Government Buildings in Ireland during my first tenure as Taoiseach. I always found Nicola a very warm person, articulate and thoughtful, and a very capable politician, who showed huge commitment to her country. She was also a true European. I wish Nicola and her family the very best for the future.”

Responding to the resignation of the First Minister, Scottish Liberal Democrat leader Alex Cole-Hamilton MSP, left, said:  “Nicola Sturgeon’s talent has undoubtedly shaped Scottish political life and she deserves to be thanked for her public service. Today is not a day for political attacks.  I wish her well for everything that comes next.

“It is to Nicola Sturgeon’s credit that she has been open about the pressures and stresses that leadership has involved.  Everyone will recognise how hard it will have been particularly to steer the country during the pandemic and the weight of those decisions.

“Scotland needs leadership that will focus on what really matters because every corner of our NHS is in crisis, the cost of living is punishing, islanders still need new ferries and education deserves to be a top priority.

“Scottish Liberal Democrats will work hard to move the debate on from the divisions of the past because people can’t wait for years behind yet more arguments about independence. Scotland needs new hope, right now.”

The Rt Rev Dr Iain Greenshields, Moderator of the General Assembly of the Church of Scotland, said: “Nicola Sturgeon is Scotland’s longest serving First Minister and has dedicated much of her adult life to public service.

“She has borne a tremendous weight of responsibility since she took office in 2014, particularly during the COVID-19 pandemic, and we wish her well for the future.

“The Church continues to uphold all elected politicians in our prayers as they seek to do their best for all people who live in Scotland and across the wider UK.”

Additional reporting by Bill Heaney