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 . 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.