Former UK ambassador to the EU outlines his hopes for more honest leadership during a speech in Liverpool

Theresa May has been accused of failing to be honest with the public about Brexit by the UK’s former ambassador to the European Union, who warned that “fantasies and delusions on all sides” risk plunging the UK into a democratic crisis.

In an excoriating denunciation of the British political class that goes to the top of government, Ivan Rogers said the Brexit debate had suffered from “opacity, delusion-mongering and mendacity on all sides” and predicted the public would not forgive politicians.

“The whole conduct of the negotiation has further burned through trust in the political class,” he said in a speech at the University of Liverpool on Wednesday. “We shall need a radically different method and style if the country is to heal and unify behind some proposed destination.”

Without naming May, he said the country required “leadership which is far more honest in setting out the fundamental choices still ahead, the difficult trade-offs between sovereignty and national control”.

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He also criticised “a secretive opaque government” that has “repeatedly failed to explain to a wider audience what the real constraints and trade-offs are” to reach the deal the prime minister has struck with the EU.

And revealing that he deplores the term “people’s vote”, he warned those advocating a second referendum that they must consider “the huge further alienation” from those who think that “their views are being ignored until they conform”.

The lecture emerged as May pleaded with EU leaders in Brussels for legal guarantees to help her sell her Brexit deal in the Commons, where she faces huge opposition. Rogers resigned as the UK’s ambassador to the EU in January 2017, following hostile briefings that depicted him as “the gloomy mandarin”. Senior government sources disliked his warnings that Brexit would be a vastly complicated process that would dominate British political life for a decade.

Since leaving the civil service, he has maintained a low profile, but has offered occasional scathing reviews of British political debate on Brexit in a series of lectures. In October he took aim at the “pinstriped Robespierres” of the anti-EU European Research Group, led by Jacob Rees-Mogg. He has also argued that British delusions and the EU’s technocratic approach mean both sides risk “sleepwalking into a major crisis”.

His latest lecture offers a stark warning about the democratic crisis that could result from a Brexit debate characterised by “evading and obfuscating choices”. Eurosceptics advocating a no-deal Brexit, he said, were “lying openly” about the extent to which World Trade Organisation rules would provide a safety net.

Criticising some of Labour’s promises on Brexit as implausible, he concludes “too much of our political debate just insults people’s intelligence”.

“We face the biggest political crisis for at least a couple of generations,” he said. “The risks are now both of a democratic crisis and an economic one.

“The public will, understandably, not for a very long time forgive a political class which, on all sides of the divide, fails to level with it on the choices being made.”

He also takes aim at the “naive” and commonly aired view of Conservative politicians that “if we just assert ourselves more aggressively in negotiations” the UK would get a fundamentally different EU offer.

Such an approach ignores that the UK is not a member state, said Rogers, a veteran of EU negotiating rooms. “Those glorious, sweaty, fudge-filled Brussels denouements are gone.”

Brexit, he stressed, would be a process not an event, invoking the example of Switzerland, which is “in a state of permanent negotiations with the EU about something highly intractable”.

The next stage of Brexit will be “whether Brexit proponents like it or not, a much longer process”.