By Ahmet Gurhan Kartal

LONDON (AA): The U.K.’s top envoy to the European Union resigned on Tuesday, creating more trouble for the country ahead of upcoming Brexit negotiations.

Britain’s Foreign and Commonwealth Office confirmed the resignation of Sir Ivan Rogers who previously claimed agreeing a final post-Brexit trade deal with the remaining EU states could take up to 10 years.

A government spokeswoman said: “Sir Ivan Rogers has resigned a few months early as UK permanent representative to the European Union.

“Sir Ivan has taken this decision now to enable a successor to be appointed before the UK invokes Article 50 by the end of March. We are grateful for his work and commitment over the last three years.”

Sir Ivan launched a thinly-veiled attack on the “muddled thinking” in Mrs May’s Government. He called on his staff to challenge “ill-founded arguments” and said that “serious multilateral negotiating experience is in short supply in Whitehall”.

He wrote to his staff to reason why he was resigning in an email: “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.”

“We do not yet know what the Government will set as negotiating objectives for the UK’s relationship with the EU after exit. There is much we will not know until later this year about the political shape of the EU itself, and who the political protagonists in any negotiation with the UK will be.”

Sir Ivan had headed former Prime Minister David Cameron’s re-negotiations with the EU in early 2016, which were later followed by the June 23 referendum which resulted in a decision to quit the European Union.

Rogers had been appointed in 2013 and his term was scheduled to end in November this year.

Prime Minister Theresa May has insisted her government will trigger Article 50 of the Lisbon Treaty, which will formally initiate the country’s exit from the 28-member bloc, despite a U.K. High Court ruling which says British lawmakers must first consult.

The May government appealed this ruling at the Supreme Court, which took it up in December 2016. A final decision is due on Jan. 9.

Additional report from agencies

[Photo: Sir Ivan Rogers. Photo by European Union official]