Health secretary Andy Burnham has been called on to keep up momentum on NHS reform.
Mr Burnham, the MP for Leigh, was until today culture media and sport secretary.
He had a stint as health minister between 2006 and 2007, when he was responsible for kick-starting debate on reforms to the minimum practice income guarantee for GPs.
He has also sat on the Commons health committee and in 1997, prior to becoming an MP, worked for the NHS Confederation as parliamentary officer.
NHS Confederation chief executive Steve Barnett said: “Andy Burnham is an excellent choice for health secretary and already knows the brief well from his previous post at the department.”
He warned the new health secretary would face “major challenges” as NHS finances were squeezed.
King’s Fund chief executive Niall Dickson said it was “frustrating” to have a new secretary of state when Alan Johnson had been in post for less than two years.
“This move has nothing to do with what is best for the health service,” he said.
“However, if a change had to be made we welcome the choice of Andy Burnham.”
Mr Dickson outlined Mr Burnham’s challenges – including the anticipated social care green paper, keeping up momentum on reform, and managing rising demand for healthcare.
He said: “A test of the new secretary of state will be his ability to display strong leadership by supporting those who have to make these difficult decisions at local level.”
Alan Johnson has been given the home secretary job in prime minister Gordon Brown’s post-election cabinet reshuffle.
Other ministers leaving the DH include health minister Ben Bradshaw, who has taken over Mr Burnham’s culture secretary role and public health minister Dawn Primarolo, who has gone to the Department for Children, Schools and Families as children’s minister. Their replacements are yet to be announced.