Edinburgh (AFP) - Scotland’s First Minister Nicola Sturgeon announced her surprise resignation Wednesday after more than eight eventful years, starting the race for a new leader to deliver on her party’s faltering campaign for independence.

In a hastily arranged news conference, the Scottish National Party (SNP) leader said in “my head and in my heart” she knew the time was right to quit.

Opponents and SNP members alike praised her towering presence in UK politics over recent years. But she departs after facing mounting pressure over her tactics for independence and over transgender rights.

The 52-year-old confirmed she would remain first minister until the SNP elects a new leader, and also stay on as a member of the Scottish Parliament until at least the next election, due in 2026.

Sturgeon insisted that her decision to step down was “not a reaction to short-term pressures” and “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,” she said.

“I am a human being as well as a politician,” she added.

“Giving absolutely everything of yourself to this job is the only way to do it. The country deserves nothing less. But in truth that can only be done by anyone for so long.”

- The independence question -

Despite that, as recently as last month she insisted she would remain first minister, telling the BBC she was “nowhere near” ready to quit after Jacinda Ardern’s shock departure as New Zealand prime minister.

British Prime Minister Rishi Sunak praised Sturgeon’s “long-standing service” and wished her “all the best for her next steps”.

The UK government’s secretary of state for Scotland, Alister Jack, called her “a formidable politician”.

But he also urged her eventual successor as SNP leader to “drop its divisive obsession with independence”.

Recognising the pivotal part played by Brexit during Sturgeon’s tenure, which she and a majority of Scots opposed, Irish premier Leo Varadkar hailed her as a “true European”.

Sturgeon’s predecessor Alex Salmond – with whom she fell out bitterly after he was accused of sexual harassment – said she left “no obvious successor”.

Salmond, who went on to form his own pro-independence party, said the onus now lay on the new leader “to reset the independence movement” after a troubled period.

After losing one vote in 2014, the SNP has been agitating for a second plebiscite, arguing that the UK-wide Brexit referendum of 2016 should allow for a fresh consultation of Scottish opinion.

But the UK government has rejected that argument, and Britain’s Supreme Court in November sided with London, leaving the SNP with no obvious course now to achieve independence at the ballot box.

- Transgender rapist -

Sturgeon has said the SNP-led government would now look to use the UK election due by early 2025 as a “de facto referendum” on separating, after more than 300 years.

But some in the SNP fear that forcing voters into such a stark choice could backfire on the party and drive up support the Labour party, which once ruled the roost in Scotland, and for Conservatives.

And opinion polls point to waning support for breaking away since the Supreme Court ruling.

Nevertheless, Sturgeon said: “I firmly believe that my successor, whoever he or she may be, will lead Scotland to independence, and I’ll be there cheering him or her on every single step of the way.”

Possible contenders in the SNP include Constitution Secretary Angus Robertson, Finance Secretary Kate Forbes, Health Secretary Humza Yousaf and Deputy First Minister John Swinney.

Sturgeon oversaw unprecedented electoral success for the SNP, but more recently appeared to have lost some of her normally sure political footing.

She faced a huge backlash after pushing through legislation allowing anyone over 16 to change their gender without a medical diagnosis.

The law would have allowed one rapist – who switched from male to female after being convicted – to serve a prison sentence in an women-only facility.

After uproar over the rapist’s case, the UK government used an unprecedented veto to block the SNP’s proposed law, exposing Sturgeon’s relative powerlessness in a touchstone case.