Treasury Select Committee chair Andrew Tyrie is pressuring the chancellor Philip Hammond to reinstate reports on how the poor are affected by the government's Budgets.
For the five years to 2015, the Treasury included “distribution analysis” in its Budget documents, which revealed how changes to tax, welfare and public spending impacted people in a range of different income brackets.
However, the analysis was dropped last year as George Osborne pushed through his planned cuts to tax credits.
In its place, the Treasury issued less detailed figures, which show changes in the share of public expenditure received and taxes paid by households, and split the analysis by quintile, rather than decile.
But Tyrie has blasted the new format as “manifestly deficient” and “a poor substitute” for the old model.
He said that the commitment to more information could reflect Theresa May's plans to tackle fiscal injustice and support Britain's low earners.
Writing to Hammond today, he said: “The Prime Minister's recent pledge to govern in the interest of the whole country, and not just the privileged few, is relevant for this disclosure.
“A high level of transparency about the effects of tax and welfare policy on households across the income distribution would seem to be a logical, perhaps essential accompaniment”