The analysis informed a Conservative party press release claiming that 94% of working households would be better off from the budget.

Will Moy, director of independent fact-checker Full Fact, wrote to Dilnot with a concern that the statistics and related analysis could not be found in the public domain.

In his reply, Dilnot agreed that this was unsatisfactory: “The analysis has not been published and is neither available to all other parties nor to members of the public.

“We regard this as unsatisfactory because of the significance that we attach to the principle of equal access to statistics and underlying analysis.”