Whitehall needs a strong centre more than ever, to keep the show on the road, to monitor the effects of leaving the European Union and to coordinate Theresa May’s government’s various (and variously contradictory) initiatives.

The Treasury has to be a pillar of that strength – yet for the past seven decades at least it has abused its power and UK government has suffered as a result, according to a damning report by former head of the civil service Lord Kerslake.

Kerslake’s report was intended to be completed by last summer but was postponed because of the political maelstrom unleashed by last June’s referendum result. It now runs up against a Brexit paradox.

The present Treasury permanent secretary Tom Scholar is different from his predecessor, Sir Nick Macpherson, just as chancellor Philip Hammond isn’t the same as George Osborne. Aside from Brexit and its implications across Whitehall, devolution is forcing (some) reconsideration of structure and attitudes at the centre.

Treasury stalwarts may be tempted to dismiss a report commissioned by the shadow chancellor John McDonnell on the grounds of his negligible chances of ever becoming chancellor. Reflecting old Whitehall jealousies they may question Kerslake’s credentials, as he said he did himself, before judging that a career as involved as his has been with practical public management before joining the civil service gives him a distinct vantage.

But those Treasury stalwarts will find themselves applauding Kerslake’s recommendation that the Treasury should live on as a unified department, despite its internal fault lines. Change would be too disruptive, he says, in the face of Brexit’s “wrenching economic changes”.

Kerslake is not asking for much in saying the Treasury’s credibility problem could be solved by more transparency and intellectual openness. Be more like the Bank of England – witness Andy Haldane’s appearance at the Institute of Government in January.

Kerslake’s institutional conservatism will disappoint those who see HM Treasury sitting squat, like the incubus in Fuseli’s celebrated painting The Nightmare, the rest of Whitehall a swooning maiden beneath its implacable gaze. The Treasury stops innovation, dampens necessary risk, pares candle ends without promoting effectiveness and efficiency, inhibits joint working and – worse – fails in what are ostensibly core tasks of macroeconomic management and running the public accounts.

Why is the UK’s productivity record so poor with such low levels of investment? Deficit and debt attest to Treasury economic management. The sparsity of financial skills across Whitehall says it has not been a great financial manager. As for its mission to secure value for money in public spending – a sniffy, uncooperative attitude towards the findings of the National Audit Office says it all.

Kerslake doesn’t explore Whitehall’s Bermuda Triangle, that dead zone bounded by the Treasury, Cabinet Office and Number 10. Would a Treasury – even one cut down to size according to Kerslake’s recommendations – ever allow the government to acquire strategic capacity and prospect ahead, providing a policy narrative to run alongside the futurology contained in Office of Budget Responsibility reports and the Whole of Government Accounts? Sir Michael Barber’s recent reappearance (as would-be chair of the new Office for Students) brings to mind the attempt under Tony Blair to make Number 10 the locus of performance management.

Take the new digital strategy. Departments will have to be cajoled, pushed and pulled if they are to move faster online and automate their transactional business. The transformation strategy emerged from the Cabinet Office but that department (a ragbag) lacks clout – except when a prime minister puts a big beast in charge, the most recent example being Francis Maude.

What if the Treasury, in monitoring allocations of money to departments, insisted as quid pro quo that they made progress on the digital front?

The Treasury does not take kindly to external review and scrutiny, said Kerslake, deadpan, at the launch of his report.

But maybe this time, with so much at stake, the odds are in favour of the top of the Treasury taking a deep breath and reflecting a little on past failings and future improvement.

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