Reality Check: Why is NHS budget data delayed by purdah?
The publication of budget deficits run up by NHS trusts in England is likely to be delayed until after the general election because of so-called purdah rules.
But what is the purdah convention and why is it controversial?
What does purdah mean?
Purdah refers to the pre-election period where restrictions are imposed on the civil service.
The rules seek to ensure that announcements and activities by public bodies do not influence the election - by putting out a stream of "good" news for example.
Purdah also restricts policy and big announcements from Whitehall, which a future government may take a different view on.
For this general election the rules kicked in from midnight on 21 April 2017.
Two years ago at the last election the head of the civil service, Sir Jeremy Heywood, explained that though the business of government continued in a normal way during a campaign, there were challenges.
He said: "We should do everything possible to avoid any activity that could call our political impartiality into question and to ensure that public resources are not used for party-political purposes."
A guidance document for the 400,000 civil servants was published by the Cabinet Office on 20 April. It sets out what is allowed and not allowed during the campaign.
It is up to the individual government departments to implement the purdah rules.
Origins of purdah
The word itself is Persian in origin and means veil or hidden away.
Dr Catherine Haddon, from the Institute for Government think tank, says parliamentary references to purdah rules date back to the late 19th Century - where ministers used the cover of purdah for not answering certain questions about the forthcoming Budget.
Why the controversy?
While the rules are designed to stop the government from putting out a stream of "good news" stories, critics argue purdah can also be used to suppress "bad news".
Last month the government lost a case at the high court. It had argued that publishing its air pollution strategy would fall foul of purdah rules, but the court disagreed.
Purdah was also under scrutiny during the Scottish and EU referendums regarding the role of the civil service in supporting the government.
But ultimately, as Dr Haddon observes: "The guidance still relies heavily on convention and interpretation."
As such, purdah is likely to remain a source of controversy.