Former cabinet secretaries condemn Tory Brexiteers for undermining Theresa May

Three former cabinet secretaries have condemned leading Brexiteers, claiming Tory backbench attacks on the government are undermining the civil service as it attempts to negotiate the UK’s exit from the EU.

Lord Armstrong, Lord Butler and Lord O’Donnell said repeated criticism of Theresa May and her Chequers proposal is jeopardising the chances of Whitehall official getting the best possible deal.

The comments from the former heads of the civil service – who have served under every previous prime minister since Margaret Thatcher – came in interviews with The Times.

Lord Butler, who served under both John Major and Tony Blair, said attacking Ms May and her advisors was not in the national interest.

His successor at Downing Street, Lord O’Donnell, said the way to ensure a good Brexit deal was not “by attacking our own officials”.

The former cabinet secretary to Mr Blair, Gordon Brown and David Cameron said forging the Conservative-Liberal Democrat coalition government in 2010 was “a piece of cake” compared with the difficult task ahead of Ms May and her most senior officials.

Lord Armstrong, the man who served under Margaret Thatcher, said the Brexiteers “who wish to undermine or frustrate” the Chequers proposal should “concentrate their fire on the organ grinder” rather than the “monkey”.

It follows Tory MP Johnny Mercer’s extraordinary attack on Ms May’s Brexit strategy earlier this week.

In an interview with The House magazine, the backbencher called her government a “s***show” and pledge to launch a “serious s***-fight” to stop the UK heading “towards the edge of the cliff”.

On Thursday the prime minister said she was considering asking the EU for an extended transition period after Brexit in a bid to break the deadlock with EU negotiators.

More than 100,000 people are expected to take to the streets of London on Saturday to make an appeal for a referendum on the final Brexit deal.

The march, organised with The Independent as part of its Final Say campaign, is set to be the largest anti-Brexit demonstration to date.