Malcolm Harrison, chief executive of the Crown Commercial Service, is to leave government for the Chartered Institute of Procurement and Supply in July.
Harrison has headed up the Cabinet Office executive agency since 2016, overseeing an annual spend of £13bn, but will leave for a role CCS said he “simply couldn't refuse”.
The Chartered Institute of Procurement and Supply, an international professional body, has more than 200,000 members in 150 countries, including high-ranking civil servants.
A CCS spokesperson said: "We will be really sorry to see Malcolm leave, but the CIPS role is one he simply couldn't refuse and we absolutely understand why he has made this decision and support him fully.
"For now, it’s business as usual at CCS and Malcolm remains very much at the helm. When the time comes in July, he will leave CCS having transformed the organisation, and set us on a clear path for continued success.
"We all wish him well in his new appointment. It is fantastic that someone with such an extensive knowledge of public sector procurement will be leading the procurement professional body in the future."
Harrison succeeded Sally Collier at CCS after her move to become chief regulator at exams watchdog Ofqual.
He has also had jobs in the private sector, including procurement roles at food and drink manufacturer Nestlé, brewing giant Anheuser-Busch InBev and the confectionary producer Mars, where he started his career.
CCS was formed in 2013 to coordinate the purchase of common goods and services for departments, with the aim of disaggregating some large contracts and opening up the market to smaller firms.
But it was fraught with flaws in implementation, and Harrison was appointed in 2016 to refocus the organisation and achieve departmental buy-in for its aims. He presided over a decision to row back on some of the commitments made by CCS when it was first established.
Speaking to Civil Service World last year, Harrison admitted to some frustration at “getting the enormous machine” that is Whitehall “to change at the place you would like it to”.
But he added: “It is a big challenge because of the environment we operate in. Do you know what? That’s half the fun.”
Announcing the appointment, Tim Richardson, chair of CIPS global board of trustees, said: “After a lengthy recruitment process, Malcolm is a very welcome addition to the CIPS team, bringing with him a wealth of procurement and leadership experience from both the public and private sectors.
“CIPS is in great shape and Malcolm will have a solid base from which to build the next phase of growth and development for the organisation.”