Iain Duncan Smith has asked civil servants in the welfare and pensions department to ignore a directive from the cabinet secretary, Sir Jeremy Heywood, which stops pro-Brexit ministers seeing government papers related to the EU referendum.
In a further escalation of the row at the heart of the cabinet, the work and pensions secretary also encouraged other senior ministers who are campaigning to leave the EU to do the same.
The move will be seen as a direct challenge to David Cameron’s authority, with with senior civil servants warning the row threatens the government’s ability to function properly.
It has emerged hours after Heywood told MPs that it was the civil service’s “constitutional duty” to support the government’s position, even if this meant restricting access for ministers who planned to campaign to leave the EU.
On the floor of the House of Commons, cabinet minister Matthew Hancock said it was an essential approach as it was the “duty of the civil service to support the government”, which is in favour of staying in the EU.
A source close to Duncan Smith confirmed reports that he would ask civil servants in his department to show him all papers related to the EU. “He has asserted his constitutional right to see everything produced in his department – including things related to the EU,” the source said.
Earlier on Monday, Priti Patel, the employment minister, who sits in cabinet, was the first to accuse Heywood of an “unconstitutional act” that “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 said.
Appearing before the public accounts committee, Heywood said that far from being unconstitutional, the civil service was upholding its primary role of carrying out government policy.
“What my letter does is put flesh on the bones of the prime minister’s own letter of the 11 January saying the government would have a position on this subject.
“The government having a position on it, it is the civil service’s constitutional duty to support the government’s position. The unusual part of this is that the prime minister is allowing several ministers in the cabinet and elsewhere to oppose that government policy,” he said.
“Civil servants won’t provide briefing and speech material for those who want to argue against the government’s position, but in every other respect they will get the full service that you would expect. It is not bypassing anybody.”
The government faced further scrutiny in an emergency Commons debate, where pro-Brexit Tory MPs claimed it could compromise the civil service’s duty of honesty.
Bernard Jenkin, a leading Tory Eurosceptic, led the rebellion with an urgent question to the government, saying the limits went further than those imposed on ministers on 1975 and created a worse atmosphere.
“Nobody objects to the government making its case in this referendum but most people expect the civil service to be impartial in carrying out its support for ministers,” he said. “It is established in law that ministers are accountable for their departments and voters expect government facts and figures to be impartial and accurate whether they are used by ministers who support remain or leave.
“So why does the cabinet secretary’s letter go far beyond the limits actually placed on dissenting ministers during the 1975 referendum?”
He was backed up by numerous colleagues campaigning for the UK to leave, including Julian Lewis, the Tory chair of the defence committee, who said the public would see “big battalions” of civil servants and spin doctors lined up on one side of the argument.
Gerald Howarth, the former defence minister, said it was a “constitutional outrage” and might give the impression that the government was “trying to rig the referendum”.
Andrew Percy, the Tory MP for Brigg and Goole, also said it was “leading people to believe there is a stitch-up to keep us in the EU”.
The criticism was not limited to those arguing for the UK to leave the EU, with a number of Labour MPs raising concerns that the decision would undermine trust in the referendum.
Tom Watson, Labour’s deputy leader, challenged the government to give its ministers free rein to run their departments or sack those campaigning against its policy.
In response to the furore, Hancock, the paymaster general, said: “All ministers can ask for factual briefing and for facts to be checked in any matter. All ministers can see documents on EU issues not related to the referendum question, as normal.
“So the guidance is clear, it’s published and the process was agreed at cabinet as the best way to manage the unusual situation of ministers who disagree with the government remaining in post.”
Ministers arguing over the role of mandarins in the run-up to the EU referendum have been warned by the union for senior civil servants that this could cause lasting damage to relationships across Whitehall.
Dave Penman, the general secretary of the FDA, the main union representing senior civil servants, said government splits over access to documents might have long-term repercussions for the way in which ministers and their officials interacted. In the short term, it could stop government functioning properly, he said.
“Politicians’ continued wrangling over this issue will only serve to impact upon the smooth running of government and damage the essential relationship between civil servants and ministers.”
He appeared to dismiss criticism from pro-Brexit ministers who claimed that Heywood’s edict would leave civil servants facing a conflict of interest.
“The FDA welcomes the clear guidance issued by Sir Jeremy Heywood, which clarifies the responsibilities of ministers and civil servants,” Penman said.
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