Theresa May's supporters have hit back at claims she was branded "lily-livered" by David Cameron after she scuppered his plans for tough new immigration controls.
Mrs May's camp took the unusual step of releasing details of her private correspondence with Mr Cameron after a new book claimed she had blocked plans to curb the numbers coming into Britain from the EU.
Mr Cameron had wanted the so-called "emergency brake" as part of his EU renegotiation in order to convince voters that he would be able to reduce immigration if Britain remained in the EU.
However in his book, All Out War, Sunday Times political editor Tim Shipman says he was prevented from doing so by Mrs May – who was then home secretary - and the then foreign secretary Philip Hammond, now Chancellor of the Exchequer.
It quotes one Cameron aide as saying: "Hammond spoke first and argued we just couldn't do something that would receive an immediate raspberry in Europe. Theresa said very, very little, and simply said that we just couldn't go against Merkel."
A "visibly deflated" Mr Cameron was said to have turned to one official and said: "I can't do it without their support. If it wasn't for my lily-livered cabinet colleagues...."
But according to the details released by the May camp, she twice wrote letters to him – in November 2014 and May 2015 – in which she argued the case for an emergency brake.
In the first she is said to have proposed the emergency brake as one of a series of measures to rebalance the rights of citizens to move within the EU so national governments can act in the best interests of their resident populations.
In the second she was said to have argued that the emergency brake was crucial to cutting numbers and convincing the public the Government was capable of policing its own borders.
Earlier, former cabinet minister Iain Duncan Smith hit back at Mr Cameron's communications director Sir Craig Oliver after he claimed Mr Cameron had been let down by Mrs May over her reluctance to come out more strongly for Remain in the referendum.
In his book, Unleashing Demons: The Inside Story Of Brexit, Sir Craig detailed 13 occasions on which Mrs May failed to support Mr Cameron before she did reluctantly "come off the fence" – but only after he gave her a dressing down over the telephone.
He said that throughout the campaign, she had pursued a "submarine strategy of disappearing from view", leading one senior Remain campaigner to ask: "Are we sure May's not an agent for the other side?"
Sir Craig acknowledged that from her point of view, the tactic had proved successful. "Amid the murder and betrayal of the campaign, one figure stayed very still at the centre of it all – Theresa May. Now she is the last one standing," he wrote.
However he was accused by Mr Duncan Smith – who campaigned for Leave - of trying to pin the blame for the failures of the Remain campaign on other people.
"Craig Oliver is one of a growing number of foolish attempts by ex-government Remainers who lost to shift responsibility for their failure," he said.
"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."