Karl Wilding will leave NCVO at the end of March after 18 months as chief executive.
He was appointed as chief executive in June 2019, and took up the role that autumn. Sarah Vibert, director of membership and engagement, has been appointed as interim chief executive.
Wilding, who has worked at NCVO for 23 years, said in a statement that new leadership was needed to "to lead the necessary cultural change NCVO is determined, rightly, to achieve".
He added that he was sad to be leaving, but confident that NCVO is "in safe hands".
Last year NCVO set up an equity, diversity and inclusion subcommittee and ringfenced funding to support it and changes to the way it works.
NCVO has just completed a strategy review and organisational restructure, reducing the overall number of staff by about one-fifth. Two members of its senior leadership team, Susan Cordingley, interim deputy chief executive with responsibility for finance and services, and Megan Griffith Gray, interim director of strategy and transformation, resigned in the autumn.
Recruitment for a permanent chief executive will begin shortly with a view to making an appointment by the autumn.
Priya Singh, who became chair of NCVO last year, thanked Wilding for his contribution and said he would with Vibert to ensure a smooth transition.
Wilding: 'It has been the highlight of my career'
Wilding said: "Following the completion of our strategy review and organisational restructure, I am stepping down as CEO of NCVO.
I am honoured to have worked for NCVO for 23 years. It has been the highlight of my career to serve as CEO for the last 18 months and work with such fantastic and dedicated colleagues.
"The board, leadership team and I are confident that, after a very challenging year, NCVO is set up for a sustainable and successful future.
"The NCVO team should all be very proud of what we have achieved over the last year. Our organisational transformation took place amid the global pandemic, which also saw us stepping up to support the sector while having to reshape NCVO in response to reduced income.
"Following some very difficult decisions, the finalisation of our new strategy and organisational structure is complete.
"But we all know there is more to do to take forward changes in how NCVO works. When I was appointed CEO, I was clear that we had to challenge ourselves to think differently and do things better. We’ve been public about our work on EDI, which shone a light on the need for deep cultural change in the organisation.
"I am proud that our new strategy and structure has cultural change at its heart. NCVO has made substantial progress over the last 18 months, but we need to go further.
"With the strategy review, organisational restructure and the first part of our work on EDI complete, now is the right time for me to step away. Sometimes leadership is about knowing when to hand the baton on and I know I am leaving NCVO in safe hands.
"I believe that new leadership will be able to lead the necessary cultural change NCVO is determined, rightly, to achieve. That requires someone new, not part of the past.
"I will leave with real sadness, but I know it’s the right and responsible decision for NCVO. I will leave at the end of March. Until then, I will work with the board and interim CEO to support them, ensuring that the organisation remains stable and focussed on the future.
"I don’t yet know what is next for me, but I will continue to be a committed champion of charities and volunteering.
"It has been my privilege to lead such a talented and committed team and to work in partnership with so many impressive agents for change across the sector."
Chair: 'The role of charities and volunteers has never been more critical'
Dr Priya Singh, chair of trustees said: "On behalf of the board of trustees, I thank Karl for his many years of service to NCVO, especially his leadership as CEO of our new strategy, his collaborative work on the response to the global pandemic and his role in initiating our EDI work. Karl’s decision to leave is rooted in his integrity and a genuine desire to do the right thing for the organisation he loves. He goes with our very best wishes.
"I am delighted to confirm the appointment of Sarah Vibert, NCVO’s director of membership and engagement, as interim CEO from today. Sarah joined NCVO in January 2020 and over the last 12 months she has had a leading role in NCVO’s internal change programme, as well as our external collaborative work to make the case for charities and volunteering during the pandemic. Sarah will work closely with Karl and the board on a smooth transition. A full search and selection process for a new permanent CEO will begin shortly, with a view to making an appointment by the autumn.
"The role of charities and volunteers has never been more critical. In turn, NCVO has an important role in supporting members and the wider sector to respond to the challenges faced by people and communities through the pandemic. You can be sure that the board and leadership team remain focussed on this vital role."