Labour arrived in power with no big idea on the future relationship with the EU, a former British ambassador to Brussels has said.

Ivan Rogers, Britain’s EU ambassador from 2013 to 2017, said Labour presented “a ragbag of issues” on the EU in its manifesto, which didn’t “remotely measure up to the challenge of the times” and would “make no measurable difference to the UK macroeconomy”.

A decade after Britain’s vote to leave the EU, Rogers said it was “close to incomprehensible” that Keir Starmer, a former shadow Brexit secretary, had sought a single market for goods “an option which the EU is always bound to reject”, because it crosses well-established red lines.

The Guardian revealed last month that the government sent a senior official to Brussels to seek a single market for goods without free movement of people, an approach likened by EU officials to Theresa May’s doomed Chequers plan.

Rogers said: “The EU is no more going to agree to ‘pick and choose’ alignment and divergence for Labour than it was for the previous government.”

One of the UK’s most experienced European diplomats, Rogers resigned in January 2017 after a Conservative party backlash over his advice about the realities of Brexit negotiations. He became a strong critic of Theresa May’s government over what he saw as failure to explain “the real constraints and trade-offs” in Brexit, then later the “diplomatic amateurism” of Boris Johnson.

In an interview with the Guardian, he said Labour came to power “unprepared” without “a serious, thought-through set of propositions” to fix what it called “a botched Brexit”.

Referencing comments made in March by the chancellor, Rachel Reeves, that cited the “deep damage” caused by Brexit and similar comments by Starmer, he said: “They are further talking up the severe damage they believe has stemmed from the version of Brexit they inherited. But there is then no coherent punchline to that analysis.”

Labour came to power promising a veterinary agreement with the EU to ease border checks, help for touring artists, and an agreement on mutual recognition of professional qualifications.

Rogers described this as “worthy technocratic fare” but “irrelevant” to the question that interests other European leaders: “Where does the UK truly see itself in the coming decade or two, and is the Labour vision really any different from a [Rishi] Sunak-type one?”

Labour’s red lines – no single market or customs union – were “massively constraining what you could ever deliver with your key trading and investment partners” he said.

The EU has said it is ready to consider British membership of the European Economic Area – the single market of 30 countries, including non-EU Norway.

Acknowledging the difficult options facing any government, Rogers said the politics around free movement of people were “hugely complex”, while British financial institutions would oppose seeing the UK a rule-taker.

“The Treasury and the Bank of England would die in a thousand ditches rather than agree a Norwegian model, where financial services provisions would essentially be set by the European Union, without us present in either the [EU] council or the [European] parliament.”

Rogers, who said he was probably “rightly regarded as the gloomiest person” near the then prime minister, David Cameron, in 2016, said he had warned EU counterparts of the risk of Brexit in 2011 or 12. The day after the leave vote, he said the EU was “ready to roll” with its response, but Whitehall was in “such a state of shock that no one is listening”.

The diplomat recalled feeling “enormous sympathy” for Cameron, who had to attend an EU summit days after losing the vote and resigning. “You know that he has just shredded his political career and here he is obliged to go through the formalities and to put on a brave face with all his colleagues.”

At that June 2016 summit EU leaders agreed the red lines towards the UK that remain fixed a decade later.

Rogers said: “I find it quite depressing that we’re still here after 10 years and still going around the same loops with the same level of misunderstandings.”