Nicola Sturgeon has resigned as Scotland’s first minister and leader of the Scottish National party after a backlash over her strategy for securing independence and a fall in popularity over proposed gender laws.

Sturgeon, who has led the SNP for eight years, told a press conference in Edinburgh that giving everything to the “best job in the world” was the only way, but that intensity could only be maintained for so long. “For me that is now in danger of becoming too long,” she said.

The 52-year-old took over from Alex Salmond as leader of the SNP in November 2014, and is the first woman to hold the position.

She said her decision was “not a reaction to short-term pressures”.

“There is a much greater intensity, dare I say brutality, to life as a politician than in years gone by.”

“It takes its toll on you and on those around you.”

Sturgeon’s authority as leader of the SNP had weakened after some of her own MPs voiced concern at her plan to use the next UK general election as a “de facto” referendum on independence.

Some feared that turning an election into a single-issue vote would cost her party votes. The SNP leadership relented and is due to hold a special conference next month when other options will be discussed.

Her popularity among Scottish voters has fallen, with a poll this week showing 42 per cent wanted her to stand down immediately. Most respondents in the Panelbase poll expressed concern over Scotland’s plan to reform gender recognition legislation, which was blocked by the UK government. She has also come under criticism for failing to say clearly whether a convicted rapist, who transitioned after committing the crimes, was male or female.

The first minister’s resignation comes even as polls showed that her party remains the most popular in Scotland.