British Prime Minister Theresa May has appointed a senior career diplomat as envoy to the European Union to replace an ambassador whose unexpected resignation rocked Brexit plans just before negotiations are due to start.

Downing Street announced on Wednesday that Tim Barrow, a former ambassador to Moscow who has previously served in Brussels, would take over from Ivan Rogers as Britain heads into the talks on Brexit.

Rogers, who resigned on Tuesday, sent an email to staff condemning "ill-founded arguments and muddled thinking" over Brexit and made it clear he was still in the dark over May's objectives.

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Barrow is not known to have taken a strong public position on Brexit.

In a statement released by May's office, he said he looked forward to joining the new government department tasked with overseeing the exit from the EU, "to ensure we get the right outcome for the United Kingdom as we leave the EU".

A Downing Street spokesperson described Barrow as a "seasoned and tough negotiator, with extensive experience of securing UK objectives in Brussels.



"He will bring his trademark energy and creativity to this job - working alongside other senior officials and ministers to make a success of Brexit," the statement added.

May intends to launch the two-year process of negotiating to leave the bloc by the end of March, beginning what is expected to be some of the most complicated international talks Britain has engaged in since World War II.