Jeremy Hunt has claimed tomorrow's planned publication of an Office for Budget Responsibility report into data provided by the last government in the run-up to March's Budget risks politicising the watchdog and is a threat to civil service impartiality.
Hunt, who was chancellor from October 2022 to July this year, set out his concerns in a letter to cabinet secretary Simon Case yesterday.
In the letter, Hunt said media reports that the new government planned to "weaponise" the report when it is published alongside the Autumn Budget tomorrow were at odds with assurances he had been given by the OBR.
Hunt also criticised the Cabinet Office's decision not to give Sunak administration ministers advance sight of the report, which he said had "no constitutional precedent".
The OBR report is expected to put meat on new chancellor Rachel Reeves's July assertions that the Sunak administration left a £22bn financial black hole. When those claims were first made, Hunt described them as bringing the civil service "into disrepute" as departmental spending plans were signed off by departmental permanent secretaries.
Independent think tank the Institute for Fiscal Studies had earlier pointed out that the Home Office routinely outlined spending plans that fell short to the tune of billions of pounds, with the balance made up through the "supplementary estimates" process.
In the letter sent to Case yesterday, Hunt said: "I am a strong supporter of the OBR and its role in enhancing the UK's economic credibility. But I hope you would agree that straying into political territory and failing to follow due process like this demeans it, and also is deeply problematic for perceptions of the impartiality of the civil service."
Hunt asked Case whether he had advised the OBR that it was acceptable to publish the report on Budget day. He also asked whether Case had advised that ministers from the Sunak administration should not be given an opportunity to comment on parts of the OBR report that could be used to criticise them.
CSW sought a Cabinet Office response to Hunt's concerns. The department confirmed that the former chancellor's letter had been received, but declined to comment further.
On Sunday, the OBR published a letter to Hunt responding to earlier questions about the plans to publish its report on the March Budget tomorrow.
OBR chair Richard Hughes said the review was concerned with the "adequacy of the information and assurances provided to the OBR by the Treasury" on departmental spending.
"The findings and recommendations solely concern the institutional relationship between the OBR and Treasury," he said. "It does not disclose advice provided to ministers nor comment on, or refer to, the conduct or decisions of ministers."
Hughes concluded that for those reasons, and after taking advice from the Cabinet Office, it was not considered "necessary or appropriate" to provide ministers of the previous government with the contents of the report before publication.
He added that "possible market sensitivity of some of the information" contained in the report was also a factor.