Ms Platt was praised for having “driven the modernisation” of the organisation, as she revealed she would leave.

Ms Platt said the time was right to hand over and focus on her other role as non-executive board member of the Financial Conduct Authority. She also chairs the FCA External Risk and Strategy Committee.

Ms Platt, who became NS&I chief executive in September 2006, has been on the advisory board of Women in Banking and Finance.

Ms Platt said: “It has been a privilege to lead NS&I through an extraordinary period for savers and the savings market. NS&I has played a key part in the UK’s fiscal strategy: we have grown the amount savers have invested with NS&I from £73 billion in 2006 to £134 billion at the end of 2015 and saved the taxpayer over £4 billion.

“Over the last decade the NS&I business model has been transformed. In 2006, half of sales came through the Post Office; today NS&I is a modern, 100% direct business with customers able to transact 24 hours a day through NS&I’s UK call centres, at nsandi.com or by post.”

Ms Platt began her career as an investment manager and managed pension funds with Mercury Asset Management before moving to BZW.

She has acted as a non-executive director of Royal London Group and has experience of being a pension fund trustee.

She said: “NS&I has an ambitious vision for continuing digital transformation and an outsourcing contract that will deliver £400 million worth of savings up to 2021. I’m particularly proud that we have been able to become increasingly self-funding by providing operational services to a growing number of other government departments such as our growing children’s hub, which will support Tax-Free Childcare payments to parents from 2017.

Economic Secretary to the Treasury, Harriett Baldwin, said: “NS&I is an important institution that has benefitted significantly from Jane’s strategic leadership over the past decade. She has driven the modernisation of NS&I and ensured that it continues to offer excellent services to millions of people across Britain.

“I want to thank Jane for the dedication, professionalism and integrity that she has shown over the past 10 years and wish her all the best in the future.”