Other countries believe Britain has “lost the plot” by pursuing Brexit because it will reduce the country’s “international influence”, says a former head of the diplomatic service.
Sir Simon Fraser also accused Theresa May of “mushy thinking” over her promise to achieve a new “Global Britain” outside the EU – branding it just a “slogan”.
Calling Brexit a “strategic error”, Sir Simon ridiculed No 10’s vow that leaving the EU would see Britain “strike out in the world”, telling a Parliamentary inquiry: “I don’t know what that means.”
And he warned: “To be frank with you, a lot of countries think, for the time being, that we have slightly lost the plot in terms of where we intend to go.”
In China last week, the Prime Minister repeatedly vowed to “build a global Britain”, arguing EU withdrawal would allow the UK to “be more outward-looking”, while retaining its strength on the world stage.
But, Sir Simon, the former Foreign Office permanent under-secretary, said: “Global Britain, at the moment, is a slogan. We need much more clarity of thought behind it.
“To be honest, at the moment, there is an awful lot of mushy thinking about this.”
Giving evidence to the Commons Foreign Affairs Committee, he warned: “Our leverage in international institutions is going to be weaker once we are outside the European Union.”
The Foreign Affairs Committee has launched an inquiry into the Government’s hopes for a “Global Britain”, following recent evidence that Britain’s international leverage is on the wane.
In November, the UK was forced to withdraw its candidate to fill a vacancy on the International Court of Justice (ICJ), because of inevitable defeat in the UN General Assembly.
Last June, EU countries helped inflict a humiliating defeat on Britain at the United Nations over the legal status of the Chagos Islands, a disputed territory in the Indian Ocean.
Before Christmas, a former UK ambassador at the UN told the same committee that he expected the EU to also refuse to back Britain in any UN votes over the Falkland Islands after Brexit.
Other countries regarded the UK's loss of influence since the Leave vote "as a shark would regard blood in the water", Lord Hannay warned.
In his evidence, Sir Simon said the UK badly needed to give “clarity” on its foreign policy after Brexit, saying: “Other countries are looking at us in a state of some concern.”
He said it would be a “huge mistake to step away from the family of western democracies that we are so closely a part of”.
And he told the MPs: “It is hard to think of an example where the European Union has stopped us doing what we wanted to in foreign policy.
“Perhaps, in the case of Iraq, it would have been good if they had.”
Sir Simon also pointed to the “meaningful vote” on the final Brexit deal, won by MPs in a pre-Christmas revolt, as the possible route to a rethink on EU withdrawal, saying: “That is assuming that we do it.”
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