The longest-serving and first female First Minister of Scotland made the shock announcement at a press conference yesterday, telling reporters that “the time is now”.

Ms Sturgeon said she will remain in office until her successor is appointed by the SNP, and refused to give any indication of who she thinks should replace her in Holyrood.

“In my head and in my heart I know that time is now. That it’s right for me, for my party and my country,” she said.

Ms Sturgeon, who has led the party following Scotland’s decision to remain in the UK, guided the country through the pandemic, and multiple election victories for her party, said that the “physical and mental impact” of the job had taken its toll.

“If the question is: can I battle on for another few months? Then the answer is yes, of course I can,” the 52-year-old said.

“Since my very first moments in the job I have believed a part of serving well would be to know almost instinctively when the time is right to make way for someone else,” she said from her residence at Bute House in Edinburgh.

“But if the question is: can I give this job everything it demands and deserves for another year, let alone for the remainder of this parliamentary term, give it every ounce of energy that it needs in the way that I have strived to do every day for the last eight years? The answer honestly is different.”

Ms Sturgeon has recently faced several political challenges, most notably within her own party, which also saw the SNP’s Westminster leader, Ian Blackford, forced to resign last year.

Most recently her government sought to push through controversial gender reforms which were blocked by Westmisnter.

The First Minister acknowledged that there had been some “choppy waters” but insisted that her resignation was not due to the “latest period of pressure” and that the recent row surrounding a transgender rapist being sent to a women’s prison was not the “final straw”.

“This decision comes from a deeper and longer-term assessment,” she said.

Ms Sturgeon refused to answer questions about whether she had been interviewed – or expects to be questioned – in a police inquiry into £600,000 of party funds raised from members to fight an independence campaign.

The First Minister took over from Alex Salmond in 2014, the political mentor with whom she would come into conflict in the years to come over the handling of sexual harassment allegations made against him.

Last year the UK’s Supreme Court ruled that the Scottish Government does not have the power to hold another independence referendum, as Westminster blocked the move.

Her surprise exit led political commentators to draw parallels with the sudden resignation last month of Jacinda Ardern as New Zealand’s prime minister.

Ms Sturgeon had planned to fight the next general election as a de facto referendum on Scottish independence, but her exit now raises questions about the immediate future of the cause itself.

But she vowed to continue as an MSP on the backbenches at Holyrood and said her life-long cause of independence is “being won”.

Nicola Sturgeon resigns following series of political setbacks