Caroline Lucas has announced that she will stand down as joint leader of the Green Party to focus on her work in Parliament and as a constituency MP.
Her two-year term of office – as joint leader with Jonathan Bartley – is due to end in September.
The Brighton Pavilion MP wrote about her decision in the Guardian newspaper.
She said: “I won’t be seeking nominations to be a candidate in this year’s leadership election, when the process starts on Friday (1 June), but instead will be focusing even more on work in parliament and in my Brighton constituency.
“I believe that Jonathan and I have shown the power of working together since we became joint Green Party leaders in September 2016 and it’s now time for me to show the power of letting go.
“I’m proud of what we’ve achieved in two very busy years: thanks in large part to the extraordinary work of staff and volunteers, the party has been transformed in so many positive ways, with progress towards our shared goals well under way.
“One of our priorities was to secure political backing for updating the party’s structures, which have changed very little since the 1970s.
“We are driving forward a root-and-branch review of how the party operates and organises itself.”
Ms Lucas, the first national leader of the Greens, from 2018 to 2012, remains the party’s sole MP at Westminster. She won her seat in May 2010.
The 57-year-old politician previously served as a Member of the European Parliament (MEP), representing South East England, from 1999 to 2010.