Mr Ackerley joined NS&I in 2017 after a career in the private sector, including as director of investments at Barclays and a spell at Virgin Money.

During his time as CEO NS&I has increased savings deposits by 42%. Funds invested by savers have increased from £147 billion in 2017 to £209 billion today.

NS&I has also invested in expanding its services to financial advisers, particularly online.

The Treasury will soon launch a hunt for a replacement.

One key change under Mr Ackerley has been the delivery of the Rainbow programme. This change strategy is moving NS&I from being a single Public Private Partnership to a multi-supplier operating model from 2024 with the aim of becoming a “more resilient, cost-effective and flexible business.”

After a career spanning 30 years, Mr Ackerley says he wishes to transition from full time work to spending more time with his family and focusing on other activities. He will take some time to reflect, he said, before deciding on his next steps.

Mr Ackerley said: “It has been a privilege to lead NS&I since 2017. I joined NS&I with a belief that everyone should have the opportunity to save confidently. 

“I’m proud of how we have delivered on this: attracting new savers by making Premium Bonds more accessible with a lower minimum purchase and making it easier to gift them to children; launching our first Junior ISA and introducing popular new customer service options like web chat.

“While the Covid-19 crisis brought its operational challenges, I’m proud that we delivered £38 billion of additional government funding in the first six months of 2020-21 – more than we had raised in the previous three years put together and approximately equivalent to the cost of the first six months of the Government’s furlough scheme.

“Above all, I am proud to have worked with such an outstanding team. Our people are passionate about delivering for our customers. It has been a privilege to work alongside them and share in their success. With NS&I’s Rainbow transformation underway, it is the right time for me to step down and hand over to my successor to take NS&I forward.”

NS&I has launched a number of new products in recent years including Green Savings Bonds in 2021 and Investment Guaranteed Growth Bonds in 2017.

NS&I chairman Ed Anderson, said: “I would like to thank Ian for all he has done for NS&I and our customers since 2017. He has ensured that NS&I delivers its core remit of raising finance for government while also meeting the needs of savers and taxpayers.

“Ian is passionate about building a savings culture in the UK and has ensured that NS&I’s products are accessible to a new generation of savers. He leaves NS&I with our Rainbow programme well underway – this will transform our business to ensure we continue to serve customers and taxpayers for many years to come.”