LONDON – Sir Ivan Rogers, the British ambassador to the European Union who unexpectedly quit on Tuesday, launched a thinly veiled attack on the government’s approach to Brexit talks in his resignation letter.

In a 1,400-word word resignation letter, published in full by The Telegraph, Rogers called on former colleagues to challenge “muddled thinking,” and “ill-founded arguments,” and called for them to “speak truth to power.” He adds that “serious multilateral negotiating experience is in short supply in Whitehall.”

Here are some key extracts from the letter (emphasis ours):

“Serious multilateral negotiating experience is in short supply in Whitehall, and that is not the case in the Commission or in the Council. The Government will only achieve the best for the country if it harnesses the best experience we have – a large proportion of which is concentrated in UKREP – and negotiates resolutely.

“Senior ministers, who will decide on our positions, issue by issue, also need from you detailed, unvarnished – even where this is uncomfortable – and nuanced understanding of the views, interests and incentives of the other 27.

“For my part, I hope that in my day-to-day dealings with you I have demonstrated the values which I have always espoused as a public servant. I hope you will continue to challenge ill-founded arguments and muddled thinking and that you will never be afraid to speak the truth to those in power.

“I hope that you will support each other in those difficult moments where you have to deliver messages that are disagreeable to those who need to hear them. I hope that you will continue to be interested in the views of others, even where you disagree with them, and in understanding why others act and think in the way that they do.”

You can read the letter in full here.

Rogers unexpectedly quit his position on January 3. He was expected to renew his position when his 4-year-term expires in November so that he could play a leading role in talks between Britain and the EU.

His shock resignation means the UK government has lost one of its most experienced and knowledgeable negotiators just weeks before withdrawal talks get underway at the end of March.

However, according to a report by The Telegraph, May is expected to appoint a new EU ambassador who "believes in Brexit." The report, citing government sources, said Rogers "jumped before he was pushed" because May had "lost confidence" in him over his "pessimistic" view of Brexit.