The UK's top diplomat in Brussels, Sir Ivan Rogers, has resigned just months before Brexit talks begin.
Then-prime minister David Cameron appointed Rogers to the role of permanent representative in 2013, and it was expected he would play a key role in negotiations for the UK leaving the EU.
Prime Minister Theresa May has said she will trigger formal talks with EU member states by the end of March.
Rogers has been accused of being a Europhile after it was recently leaked that he told May that Brexit would take a decade to negotiate.
His resignation comes as a further blow due to fears that the UK is lacking in experts to help negotiate trade deals with the EU.
Rogers has previously served as private secretary to then-chancellor Kenneth Clarke and prime minister Tony Blair.
Labour MEP for London, Seb Dance, said the UK needed Rogers:
Labour MEP for the north east, Paul Brannen, said:
Former permanent secretary to the treasury, Nick Macpherson, said:
Labour peer Janet Royall said his resignation is understandable:
And if you thought it couldn't get worse, MEP Gerard Batten, UKIP's Brexit spokesman, has suggested a replacement.
He writes in a blog post:
Perhaps Nigel Farage would consider taking up the post?
After all he ably demonstrated in the Referendum campaign that he knows more about the EU than any other British politician, and he can be relied upon to defend Britain’s interests.