Mr Bell, who built up and floated the platform on the stock market, will remain on the AJ Bell board as non-executive deputy chair from the same date.

Mr Summersgill has been with AJ Bell since 2007 and is currently deputy CEO. He has also been chief financial officer since 2011. He will be succeeded as CFO by Peter Birch on 1 July.

The company says the appointments are in line with the board’s long-term succession planning. 

Mr Summersgill has held several executive roles at AJ Bell and has also contributed “significantly” to the company’s rapid growth, the Manchester-based firm said. 

He play a key role in helping float the company in December 2018 via an IPO. 

Mr Bell founded the firm in 1995. He will continue to be “actively involved” in evaluating future market developments and opportunities as well as “campaigning for fairness and simplicity for UK retail investors and financial advisers,” the company said.

Mr Bell said: “It has been an honour to lead AJ Bell as CEO, both as a private company for many years and more recently as a publicly listed business. I would like to thank our people, past and present, for helping to grow AJ Bell into the business it is today. It has been a fantastic journey so far and I am as excited as ever about the prospects for the AJ Bell.

“I am delighted to be handing over to Michael, who has already proven himself to be an outstanding leader within the company. It has been a pleasure to work alongside him for over a decade and I know he is the right person to drive the business forward with passion, enthusiasm and integrity.

“I look forward to moving into a new role of deputy chair, where I will continue to support Helena, Michael and the rest of the team as we look to capitalise on our significant long-term growth opportunity.”

Mr Summersgill said: “It is a huge privilege to be take over the CEO role from Andy. We have built the company into one of the largest investment platforms in the UK and I am incredibly excited by the growth opportunity ahead of us. 

“The foundations for us to deliver long-term growth in both the advised and D2C markets are firmly in place. My focus will be on continuing to evolve our platform propositions and service capabilities to meet the ever-changing needs of advisers and customers. I am confident we have the right team in place to meet those needs and remain at the forefront of the investment platform market.”

AJ Bell chair Helena Morrissey said: ““Michael’s appointment as CEO of AJ Bell is the culmination of a long-term succession process that the board has been running for a number of years. The board concluded that Michael was the standout candidate given his experience of the business and the market.” 

“I am delighted that Andy will continue to serve on the board as deputy chair. He has built AJ Bell into one of the UK’s leading investment platforms and will remain an important member of the Board. He has provided great support to me since I joined the company in 2021 and I look forward to working alongside him in his new role as we strive to deliver AJ Bell’s long-term growth strategy.”

• AJ Bell's latest figures for the half year published in May showed a fall in pre-tax profit to £26.1m (HY21: £31.6m) for the six months ending 31 March. AJ Bell attributed the fall to a drop in retail investor engagement and dealing activity, which was "exceptionally high" last year. Advised assets at the end of the half were £46.5bn (FY21: £45.8bn). The platform saw an 8% rise in advised customer numbers to 137,201 and a 10% rise in direct customers. Total retail customer numbers rose 35,555 to 418,309.

Financial Planning Today Analysis: The decision by AJ Bell founder Andy Bell to stand down from the CEO role may have surprised outsiders but insiders would have been expecting it. The company has long had a robust succession plan in place with Michael Summersgill the likely candidate for some years. Andy Bell will remain a significant figure at AJ Bell for many years, not least because he still owns a significant chunk of the firm he founded 27 years ago. Andy Bell has been a pivotal figure at the firm which started its growth strategy by building a serious presence in the low cost SIPP market before expanding rapidly with its low cost platform offering. He should rightly be proud of the rapid growth of the firm in recent years, both in the adviser and D2C market. This is a difficult space to cover but AJ Bell has built a formidable platform presence despite being far from the largest platform. It now serves well over 400,000 customers and further growth will be a target but there is a long way to go before it catches up with Hargreaves Lansdown, which has 1m more customers. The company has recently turned to TV advertising so expect to see a higher national profile as AJ Bell and others target a new generation of post-pandemic younger investors. Recent news from the company has also suggested a focus on the younger investor market, to be reached via a new app and other tools. This does not mean that the company will turn its back on the adviser market, which remains supportive, but it does mean the company's distribution will change. Mr Bell's baby is getting older but will look on as a proud parent. The challenge now for AJ Bell will be to move on from its low cost roots to become a bigger, more rounded business. Keeping costs and prices low and building scale will be a challenge.