Allies of Theresa May have released details of letters they say the then home secretary wrote to David Cameron making the case for an emergency brake on EU migration amid negotiations before the Brexit referendum, rejecting charges she did not back him on the issue.

The unusual move happened after May came under criticism for her role in the EU vote in two new books.

One, by Cameron’s former communications director, Sir Craig Oliver, said May frustrated the remain campaign by pursuing a “submarine strategy” of disappearing from view.

Another book by the Sunday Times political editor, Tim Shipman, said May had failed to back Cameron over his desire to call for an emergency brake that could limit the extent of EU migration when he set out his goals to renegotiate with the EU in November 2014.

The book says Cameron was persuaded against this idea at a meeting with May and Philip Hammond, now chancellor, who was then foreign secretary. Cameron described May as “lily-livered” for giving this advice, the book claims.

However, May’s allies have given details of two letters from May to Cameron in which, they say, she recommended seeking an emergency brake. One was sent on 21 November 2014, a week before the reported meeting between May, Cameron and Hammond. The other was dated 21 May 2015.

The allies say these called for stronger immigration controls, something May was on the record as seeking at the time. It was “bizarre and untrue” to suggest May was weak on the issue, her allies say.

The letters form the latest salvo in a proxy war of words between the current and former prime ministers, told through the new books and the input of various allies.

It comes at a time of deteriorating relations between those close to the new prime minister and allies of Cameron, who are furious at her for distancing herself from his prime ministership and ditching key aspects of his legacy.

Philip Hammond attended the meeting with David Cameron and Theresa May. Photograph: Laura Lean/PA

May came out for remaining in the EU early on but kept a low profile in the referendum and made only one public intervention in favour of the in campaign. Since becoming prime minister, she has been adamant that “Brexit means Brexit”, signalling she is fully committed to taking the UK out of the EU.

Oliver’s book, serialised in the Mail on Sunday, recounted that Will Straw, the director of the remain campaign, had been so uncertain where her true loyalties lay, he sent a text asking: “Are we sure May’s not an agent for the other side!?”

The former communications chief was strongly criticised on Sunday by Iain Duncan Smith, the former work and pensions secretary, who said he should not blame May for the failure of the remain campaign and called on him to “stop carping” and show humility in the face of defeat.



Duncan Smith said: “In the past, a knight of the realm who had failed in battle and lost would have quit the field and retired in humility to better understand their own failings. How surprising then to find that far from that, Sir Craig Oliver, one of the leading lights of remain, has decided to instead try to pin the blame for his failure on others, particularly the new prime minister.”



Oliver described one conversation after Cameron had sounded out May about her views on the EU. “It sounds like she refused to come off the fence. From her point of view it’s a smart strategy, trying to demonstrate she is her own person, allowing her to have her cake and eat it, but it doesn’t seem fair on DC, who has treated her well,” he wrote.

There was further concern within No 10 when May was “playing her cards close to her chest” during a conversation about the EU in cabinet. “Her sphinx-like approach is becoming difficult, with the press questioning which way she will jump. The conversation turns around this being the biggest thing the PM has faced and him not even knowing if the home secretary is backing him,” he wrote.

Cameron ended up telephoning May during a train journey to Chippenham for a speech and demanded she make her position clear. “When he hangs up he seems to think he’s made an impact,” Oliver wrote. “Later, the home secretary issues a statement saying she believes there’s ‘the basis for a deal here’.

“This is interpreted as the moment she climbed down off the fence. After all the concern around her, it all seems to have ended not with a bang, but a whimper.”

Duncan Smith said: “Craig Oliver’s is one of a growing number of foolish attempts by ex-government remainers who lost to shift responsibility for their failure. The grown-up thing for them to do, instead of carping, is to show some humility and get behind Theresa May as she seeks to get back control of migration with the EU as we leave.”