Those ministers who support leaving the EU are understandably aggrieved at the decision – apparently jointly taken by Downing Street and Sir Jeremy Heywood – to deprive them of full access to their own civil servants. It would be bad enough to forbid them from calling on their civil servants for advice (their predecessors in 1975 were allowed to do so) but to order civil servants not to show them EU-related documents is absurd.

Priti Patel has today said that:

“Jeremy Heywood’s unconstitutional act threatens the reputation of the civil service. Secretaries of State are responsible for their departments. For an unelected official to prevent them being aware of the information they need for their duties is wrong.”

She is correct for several reasons.

In our organic constitution, ministers are held responsible for all their departments’ actions. Banning them from knowing what their departments are up to is wholly inconsistent with that principle – they can’t be accountable and simultaneously forbidden from knowing what they’re accountable for. Will Downing Street now take the blame for anything going wrong instead? I rather doubt it.

The decision also seems irresponsible on the Government’s own terms. Our membership of the EU is, we are told, key to the fight against terrorists. How then can it be safe to forbid the Justice Secretary from seeing Ministry of Justice documents relating to the EU’s supposedly vital counter-terrorism activities?

Politically, this is another serious error. It was the Prime Minister who told his colleagues that they would be free to campaign “with their heart” on the referendum question, at no risk to their ministerial position. He was right to do so, both for the sake of a fair referendum and in order to preserve Party unity in a post-referendum world. This new policy to gag and undermine ministers who support Leave Remain clearly runs counter to both the letter and the spirit of his promise.

Not only is future Conservative unity at stake, so is the Government’s reputation. At the last election, Cameron’s theme of quietly capable, sensible government was worth a great deal. He has long prided himself on placing pragmatism ahead of personal or ideological concerns. Any action which seeks to hobble good ministers in going about their work is a threat to that reputation – and to the good governance of the country.

Like the Prime Minister’s jabs at Boris Johnson a week ago, this attack on Tories who support Leave is unnecessary, unjust and ultimately self-defeating. The Government would have been wise not to indulge its worse instincts in the first place – it has begun to do so, but there is still time to recognise the error and change tack.