Andrew Stephenson has been appointed minister for HS2 – the high-speed rail link connecting London with Birmingham, Manchester and Leeds.
He was already the rail minister with responsibility for the Transpennine and Northern Powerhouse Rail routes.
Earlier this month Boris Johnson said he would appoint a minister to “restore discipline” to HS2.
It has come under fire over spiralling costs, but supporters say it will rebalance the economy.
The prime minister gave the project the go-ahead last week but acknowledged it had been “a controversial and difficult decision”.
Labour supports HS2 but has criticised an “abject failure of successive Conservative governments to keep on top of the costs”.
The cost of the programme set out in the 2015 Budget was just under £56bn, but one independent estimate puts it as high as £106bn.