Chris Chant, the director of the government's G-Cloud programme, is set to retire at the end of the month.
He will be replaced by Home Office CIO Denise McDonagh, it is understood.
Chant, who has been assertive in his drive to change the way government buys IT, yesterday posted a blog blasting many of the government's chief information officers. He wrote that a number were not capable enough to make the changes needed in public sector IT.
The Cabinet Office said in a statement: "We are very thankful for the years of service and in particular, his recent success with the G-Cloud Programme. Chris leaves Government ICT in a strong position and we wish him all the best in the future."
It added that "the G-Cloud programme will continue following his departure", and that a decision on who to appoint next "will be made in the coming weeks".
Last week, the government appointed Liam Maxwell as deputy government CIO, reporting to CIO Andy Nelson.