Special report by His Majesty's Government in the United Kingdom of Great Britain and Northern Ireland to the Council of the League of Nations on the progress of 'Iraq during the period 1920-1931 (pdf)
It would appear that the document you are looking for has the reference TNA/ CO 730/167/14; Report to the League of Nations on the progress of Iraq under the mandate.
It has not been digitised so you you will need to either order a pdf direct from the NA, or hire a researcher to obtain it for you
Could you supply the original source supplying the reference to this document, and it's context, just to confirm the details?