The new Levelling Up Secretary will also serve as Minister for the North, the Tory party chairman has said.
There was some doubt over whether Liz Truss would follow through on her reported pledge to create the position, with Labour and Cooperative MP Simon Lightwood calling for clarity earlier on Wednesday.
In a letter to the new PM, he said he hoped she had not “reneged” on her promises.
The Northern Research Group of Tory MPs previously said Ms Truss, along with other leadership contenders, had signed up to its “Northern Agenda” pledges – which included creating the ministerial role.
Mr Lightwood wrote: “On Tuesday 12 July, you signed up to the pledges of the Northern Research Group, agreeing that you would appoint a Minister for the North, with ‘direct responsibility for local growth and levelling up, who has a seat at the Cabinet table and the levers of a department for growth at their fingertips’.
“It is incredibly disappointing to see that no such minister has been appointed to your Cabinet.
“I hope that this will be urgently rectified, and that you have not reneged on your pledges already.”
Jake Berry, the new party chairman, later said Simon Clarke has assumed the post.
He told ITV’s Peston: “The Prime Minister’s been absolutely clear that she will have a fiscal event later this month, but, you know, we’ve got a Levelling Up Secretary in Simon Clarke, who is also the Minister for the North.”