Theresa May’s former chief of staff has accused the UK’s chief Brexit negotiator, David Frost, of having a “brass neck” after he said the UK government had “blinked first” in negotiations. Gavin Barwell, a key member of the former prime minister’s negotiating team, said Boris Johnson’s withdrawal agreement was “95% the work of his predecessors” and a deal had only been secured by conceding to the EU’s demand for some customs checks between Northern Ireland and the rest of Great Britain, which May’s team had not agreed to. Lord Frost, who will host another crunch round of negotiations in London this week with the EU’s Michel Barnier, told the Mail on Sunday that the UK would leave at the end of the transition period in December “come what may” and would not agree to being a “client state.” Informal talks between the pair have not yielded any breakthrough in what one EU diplomat said was “a wasted summer”. Barwell was angered by comments by Frost in the interview in which he said:“We came in after a government and negotiating team that had blinked and had its bluff called at critical moments and the EU had learned not to take our word seriously. “So a lot of what we are trying to do this year is to get them to realise that we mean what we say and they should take our position seriously.” Barwell tweeted that it had in fact been Johnson’s team, including Frost, who had blinked. “Given the Withdrawal Agreement & Political Declaration David Frost negotiated last autumn were 95% the work of his predecessors – and the 5% that was new involved giving in to the EU’s key demand (for some customs processes when goods move GB to NI) - that quote’s some brass neck,” he said. Two key differences remain between the UK and the EU: fishing rights and state aid, the level of taxpayer support the government can give to UK businesses. Speaking on Sunday, the foreign secretary Dominic Raab said a deal was “there for the taking”. “I think this week is an important moment for the EU to really effectively recognise that those two point of principles are not something we can just haggle away – they are the very reasons we are leaving the EU – but we want a positive relationship and the arm of friendship and goodwill is extended,” he said. “It is up to the EU to decide whether they want to reciprocate.” In his interview on Sunday, Frost ruled out accepting level-playing-field terms that “lock us into the way the EU do things”. He said Downing Street had created a “transition hub”led by Cabinet Office minister Michael Gove to prepare for a no-deal Brexit from January 2021, something government officials have termed an “Australia-like arrangement”. “Obviously, lots of preparation was done last year. We are ramping up again, and have been for some time under Michael Gove’s authority,” Frost said. “I don’t think that we are scared of this at all. We want to get back the powers to control our borders and that is the most important thing. If we can reach an agreement that regulates trade like Canada’s, great. If we can’t, it will be an Australian-like trading agreement and we are fully ready for that.”