In an open letter to Secretary of State, Peter Hain MP, Mr Williams set out what he believes should be the new Children's Minister's agenda.
"Children and young people's lives are affected by several Government departments," said the Commissioner. "It is important that departments work together, complementing their efforts."
In his letter to the Secretary of State (published here today) Mr Williams outlined some of the key areas he believed needed to be addressed.
He also expressed his desire to make sure there is a more joined up approach for children within Government.
"We are sometimes frustrated by the lack of progress on some key policy areas, which fall between a number of government departments," said Mr Williams. "I hope that the Children's Minister will be able to draw Ministerial colleagues and officials together to progress these issues."
The Commissioner gives, in his letter, several examples, including Speech and Language Therapy Services, Child Protection and Vetting, Play, Early Years Provision and Extended Schools.
"I have no doubt that Lord Rooker faces a challenging agenda, but I believe it is essential that this agenda is tackled quickly and efficiently, and welcome the opportunity to work with the new Minister" said Mr Williams.