The UK-based Professor Ted Malloch has reportedly been interviewed for the EU ambassador role and is expected to be appointed following the confirmation of Rex Tillerson, the US secretary of state-elect.
The 64-year-old academic was reportedly recommended to US President Donald Trump by Nigel Farage, the former Ukip leader.
He has angered some with his reported comments about the EU and his prediction that the single currency could collapse "within 18 months."
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German Socialist MEP Jo Leinen has now broken ranks by publicly calling for his nomination to be vetoed.
Leinen said, "The European Union should refuse to accredit the designated US ambassador to the EU, Ted Malloch."
Leinen said that Malloch's latest reported remarks about the EU "show he is unfit for the job."
He added, "I have been horrified by some of the things Malloch has been saying in the press. This is the language of Nigel Farage and he has discredited himself from the outset. His nomination would have to be ratified by the Commission, Council, EEAS and all member states and, given what he has said about the EU, I do not think that is likely.
"He seems to have a strange perception of the EU and what it is about. I think that to have a US ambassador who is openly against the core principles of the EU should set the alarm bells ringing. There is still time for the EU to look closely at this nomination but I certainly hope that he is not chosen."
Leinen insisted Malloch should not be offered the job, adding, "What we don't need now is an obstructionist who dreams of the end of the euro and of taming and wrestling down the EU like he allegedly did with the Soviet Union."
Malloch, who worked for the United Nations in the late 1980s, has never held back his contempt for the EU.
The former Oxford University professor said that the UK and US could cut a bilateral trade deal in 90 days and that elections in Europe this year could sweep away the EU as we know it.
"The one thing I would do in 2017 is short the euro," Malloch told the BBC, "I think it is a currency that is not only in demise, but has a real problem and could in fact collapse in the coming year, year and a half."
He recently predicted that the EU would back down over its refusal to negotiate an early trade deal with Britain.
On Monday, Malloch told this website that he was unable to comment on the EU job until his nomination is confirmed.