He will be replaced on a temporary basis by Malcolm Gomersall, chief operating officer, who will take over the day-to-day running of the firm alongside his current role while a CEO selection process takes place.

Dunckley took the decision to step down over Christmas in order to take a break after five years as head of the firm.

He is set to retire but will remain as a partner in the firm until the end of March to help ensure a smooth transition.

In March 2022, Dunckley was re-elected as CEO for a second four-year term, and this was due to last until 2026.

The firm said he had ‘made the decision to step down now because the firm is well placed to manage the transition to new leadership’.

Gomersall will lead the firm until a successor is appointed. He has been COO since 2019 and has spent 22 years at the firm.

Dunckley first joined Grant Thornton in 1998 and was made partner in 2006. Before being elected as CEO he held a number of senior leadership roles including global head of recovery and reorganisation, head of the national recovery team and led the mid-market business in London. He originally trained as a chartered accountant at Hunter & Rawlinson.  

During his tenure, he led the firm through the pandemic, attracted new clients from across the public and private sectors, and made significant investment in staff and culture. The decision was also taken to withdraw from handling FTSE listed audits and has invested significantly in the audit team and technology to improve the quality of the firm’s audit activity. It has also allowed the firm to pick up new business where Big Four firms have client conflicts.

Grant Thornton reported 12% net revenue growth to £610m for year end 2022 and 5% profit growth to £121m. This was a significant improvement on performance in 2020 when the firm reported £482m in fee income. The 2023 results are due to be published this spring.

Dunckley said: ‘The firm is at a high point. We will announce our results in the spring and, while I cannot share the detail, we expect to announce another strong year. I can confidently praise the considerable contribution everyone at this firm has made over the last year, and throughout my tenure as CEO.

‘Grant Thornton is a brilliant firm, and I am immensely proud of what we have achieved over the past five years. We are trusted to deliver outstanding work for our clients. And we are operating through a period of significant change and growing demand for our work.

‘Over Christmas, I decided it was time to take a break, following a successful five years’ service as CEO. I am confident that I pass a quality operation into the safe hands of my successor and all our partners.’

Commenting on the decision, Imogen Joss, chair of the Grant Thornton partnership governance board, said: ‘I know everyone at Grant Thornton will join me in thanking Dave for the significant contribution he has made to the firm. We wish him every success for the future.

‘I am delighted Malcolm has agreed to take over the day-to-day running of the firm. It is testament to Dave’s leadership that we have such a strong team in place to take the firm forward.’

Gomersall said: 'I want to thank Dave for his service to Grant Thornton. Under his leadership, the firm has had its most successful period in its history in terms of its financial performance and delivering market-leading audit quality. It has been a pleasure to work together, and he leaves the firm well placed to continue to grow and succeed.

'We have strong foundations in place, and the market presents significant opportunities for our people and clients over the years ahead.'