London: Ivan Rogers, Britain's ambassador to the European Union, resigned on Tuesday just weeks after he was criticised over a leaked memo stating that Brexit could take longer than expected to sign off, the media reported.
Rogers, who was appointed to the role of permanent representative by David Cameron in 2013, had been expected to play a key role in Brexit talks expected to start within months, the BBC reported on Tuesday.
The British Foreign Office did not give reasons for his departure.
According to reports, Rogers did not explain the reasons behind his decision when he informed staff of his decision to leave early.
He played down his resignation by stating it was only slightly ahead of his planned departure date.
The news has prompted concerns that Britain will get a worse Brexit deal than it would have done if he was part of the team, said the report.
Charles Grant of the Centre for European Reform said in a tweet: "Ivan Rogers' resignation makes a good deal on Brexit less likely. One of the very few people at top of Brit government who understands [the] EU."
According to the BBC, Rogers in December had privately told ministers a Britain-EU trade deal might take 10 years to finalise. He told them this was also the view of the other 27 member states.
Rogers had been due to leave his post in November 2017.
Labour MP Hilary Benn, who chairs the Brexit select committee, said his resignation had come at a "crucial" point and urged the government to "get its skates on" in finding a replacement.
"It couldn't be a more difficult time to organise a handover," he added.
Reacting to the news key Brexit-supporting Tory MP Steve Baker said: "We wish him well... now look forward to a UKREP appointment which will ensure an uninterrupted run at the Brexit process."
Updated Date: Jan 03, 2017 22:01 PM